We've all gotten to see Henry Brand's version of this deck, and the best pre-worlds variant IMHO is Zachary Krekeler's variant on this site. I have personally tested Krekeler's version of this deck, and while watching Worlds, Brand's version looked like it ran smoother comparitively.
However, what I can't figure out or at least can't decide on is if Brand's deck was only specifically tuned for World's meta, and if so, I feel that Krekeler's deck may do better in the wild and lower tier competitions where you'll get more weird stuff.
Here's my cross-analysis of the core deck so far. If we strike on anything that seems assured, I'll update this post for new people
Pokemon
3 Mewtwo & Mew GX
3 Dedenne GX
1 Cobalion GX
1 Latios GX
1 Jirachi GX
1 Reshiram & Charizard GX
1 Naganadel GX
1 Marshadow
Variations:
+1 Mewtwo & Mew GX
1 Espeon & Deoxys GX
1 Magcargo GX
1 Solgaleo GX
1 Dragonite
1 Altaria GX
1 Greninja GX UNM78
1 Greninja GX PRSM201
1 Mew
2 Venomoth GX
Trainers
4 Welder
4 Pokegear 3.0
4 Custom Catcher
4 Cherish Ball
3 Acro Bike
2 Mysterious Treasure
1 Fire Crystal
Variation
4 Janine
+2 Fire Crystal
2 Pal Pad
1 Heat Factory Prism Card
1 Veridian Forest
2 Switch
1 Electromagnetic Radar
+1 Acro Bike
+1 Mysterious Treasure
Energy - 11
7 Fire Energy
Variation
+1 Fire Energy
3 Psychic Energy
4 Rainbow energy
I'll probably go over this again for formatting.
My thoughts on the deck and variants in addition to what has already been said:
+Mew3:
I so far have not had an issue where I didn't quickly get a Mew3. I feel that 3 is a good number in the deck so far. Probably don't need a 4th unless you want to really make sure you get one to start.
Cobalion GX:
With rainbow energy this guy makes sense to me for the Metal Symbol to deny things like RaiTwo, but the only reason I can see to include him in Grant's deck is for the Iron Rule GX move. Given that there are other options available to deny damage, I am not seeing a good reason to include it without the rainbow energy. However, I can see maybe a timely denial of a non-damaging attack. Great with rainbow energy, not great without.
Espeon & Deoxys GX
This guy strikes me as a bench warmer backup or a back bench sniper option. Psychic club may be nice, but I so far feel like I end up with Reshizard and a Dedenne more often than not, which caps this at 100 damage. While not terrible, but for that price range in energy, there are far better options, and this guy could just as well be in the discard pile as not. I feel the sniping is better served by the Greninja below. I'll probably leave him out.
Magcargo GX vs Dragonite GX
Since he can't sit on your bench, the only reason to have this guy is for the power up knockout ability with Lava Flow. Since you have to discard energy to use lava flow, I feel Dragonite GX would be a better choice for a heavy hitting knock out. Since to knock out a Reshizard, you'd need to mill 6 energy, or just 3 with Dragonite. Further, I have found the Mach delivery VERY handy in turn 1 a couple times when I wasn't getting the cards I needed to go through my deck. Dragonite is the way to go IMO.
Healing: Solgaleo GX vs Mew3 vs Greninja GX FBL24
These are our primary choices for getting damage off of us. Solgaleo gives us a cheaper option to just remove damage, and comes with an ability to recover energy from the discard which would allow us to need fewer Fire Crystals in play. Greninja has a cool ability which does damage and pulls the whole guy back into our hand, and has a GX bench sniper ability. Lastly, we have the 200 damage full team heal provided by Mew3 itself. Plenty of staying power in this deck. I'll be taking both I think.
Greninja GX PRSM197 vs Altaria GX
Both of these guys have an ability to chew through special defenses similar such as Altaria's Bright tone. Greninja's strength is that he can do it with one rainbow energy, and Altaria needs two rainbow energy. Which puts Altaria as the lead offensive card. However, Altaria has a defensive move for two energy that blocks GX and EX moves which seem to be the majority of the meta, but I am starting to see more non-GX decks. Neither seem absolutely necessary but both add nice utility. If I can only take one, I'd lean towards Greninja for more offensive capability. Especially if we work in Venomoth.
Mew
He sits on your bench and protects the other bench warmers from getting sniped. If your opponent wants to kill him or get around him, they'll have to burn their custom catchers to do it. IMO he is missing from Grant's deck and belongs in yours too.
Defense: Venomoth GX
I won't spend much time on this beyond my personal observations since Krekeler and Manley cover it pretty well in their articles. I personally find the utility of the shinobi mastery a bit swingy, and am considering removing them if I can't find the space to fit them in with my modifications. I will definitely say that it is a nasty mechanic when it comes together. My favorite moment was knocking out a pokemon, and them moving their fully powered reshizard into attack position, and then... nothing. Next turn Dragonite for the win. I totally felt (imagined) their jaw drop to the ground when they realized what happened. Every other match, it doesn't seem to have made or broke my deck.
On to trainers
Janine
If you're not running the venomoth combo, there are better options. Not much more needs said other than she's a better than average consistency card, but there are definitely even better in a vacuum. Such as:
Bill's Analysis
This goes in the deck if you don't run Venomoth. This helps you fish out all the other trainers, stadiums, etc you need, but doesn't really fit in your deck alongside Janine IMO.
+Fire Crystal
If you're running the Solgaleo, you probably only need 1 or 2, because you hopefully won't lose more than a single mew3.
Heat Factory Prism Card vs Veridian Forest
Personally, I have never felt it was a preferential situation to lose a fire energy to draw more. Maybe I haven't been quite desperate enough, but the consistency so far has not made it bad enough. So, I'd not choose Heat Factory normally, however... I'm pretty sure Grant picked Veridian Forest as a way to fish out his psychic energy, and that makes the choice moot since I'm on team Rainbow Energy. The only other stadium cards that are even a potential option is a 4th Giant Hearth or Sky Pillar. Heat Factory it is due to lack of good options.
Switch
I feel like a couple of these were amiss from Krekeler's deck. There have been times I have needed or desperately wanted a switch and didn't have it or even the option of getting it. I'll be adding a couple of these.
Electromagnetic Radar
The only reason to have this in the deck is to fish out Dedenne and use it to more rapidly discard cards to feed your Mew3. With 3 Dedenne, I haven't had issues getting one, and usually end up with a couple at the end that I don't need. Take it if you can fit it, but don't worry too much if you can't.
+Acrobike & +Mysterious Treasure
Both of these feed the consistency engine. If you can't fit them, you can probably do without the extra, but it wouldn't hurt to have them either.
Lastly, Energy
I am fully on board with 4 rainbow energy and 7 Fire energy for 11. I have not ever felt the hurt for energy in Krekeler's deck, and I plan to keep it the same.
So where does that leave us with a post world's deck list? I have 15 cards to play with from what I feel is necessary, and I've smooshed this out.
Pokemon: 18
3 Mewtwo & Mew GX
3 Dedenne GX
1 Venomoth
1 Cobalion GX
1 Latios GX
1 Jirachi GX
1 Reshiram & Charizard GX
1 Naganadel GX
1 Marshadow
1 Mew
1 Dragonite GX
1 Solgoleo GX
1 Greninja GX FBL
1 Greninja PRSM197
Trainers: 31
4 Welder
4 Pokegear 3.0
4 Custom Catcher
4 Janine
3 Cherish Ball
3 Giant Hearth
3 Acro Bike
2 Mysterious Treasure
2 Switch
1 Fire Crystal
1 Heat Factory Prism Card
Energy: 11
7 Fire Energy
4 Rainbow Energy
However, what I can't figure out or at least can't decide on is if Brand's deck was only specifically tuned for World's meta, and if so, I feel that Krekeler's deck may do better in the wild and lower tier competitions where you'll get more weird stuff.
Here's my cross-analysis of the core deck so far. If we strike on anything that seems assured, I'll update this post for new people
Pokemon
3 Mewtwo & Mew GX
3 Dedenne GX
1 Cobalion GX
1 Latios GX
1 Jirachi GX
1 Reshiram & Charizard GX
1 Naganadel GX
1 Marshadow
Variations:
+1 Mewtwo & Mew GX
1 Espeon & Deoxys GX
1 Magcargo GX
1 Solgaleo GX
1 Dragonite
1 Altaria GX
1 Greninja GX UNM78
1 Greninja GX PRSM201
1 Mew
2 Venomoth GX
Trainers
4 Welder
4 Pokegear 3.0
4 Custom Catcher
4 Cherish Ball
3 Acro Bike
2 Mysterious Treasure
1 Fire Crystal
Variation
4 Janine
+2 Fire Crystal
2 Pal Pad
1 Heat Factory Prism Card
1 Veridian Forest
2 Switch
1 Electromagnetic Radar
+1 Acro Bike
+1 Mysterious Treasure
Energy - 11
7 Fire Energy
Variation
+1 Fire Energy
3 Psychic Energy
4 Rainbow energy
I'll probably go over this again for formatting.
My thoughts on the deck and variants in addition to what has already been said:
+Mew3:
I so far have not had an issue where I didn't quickly get a Mew3. I feel that 3 is a good number in the deck so far. Probably don't need a 4th unless you want to really make sure you get one to start.
Cobalion GX:
With rainbow energy this guy makes sense to me for the Metal Symbol to deny things like RaiTwo, but the only reason I can see to include him in Grant's deck is for the Iron Rule GX move. Given that there are other options available to deny damage, I am not seeing a good reason to include it without the rainbow energy. However, I can see maybe a timely denial of a non-damaging attack. Great with rainbow energy, not great without.
Espeon & Deoxys GX
This guy strikes me as a bench warmer backup or a back bench sniper option. Psychic club may be nice, but I so far feel like I end up with Reshizard and a Dedenne more often than not, which caps this at 100 damage. While not terrible, but for that price range in energy, there are far better options, and this guy could just as well be in the discard pile as not. I feel the sniping is better served by the Greninja below. I'll probably leave him out.
Magcargo GX vs Dragonite GX
Since he can't sit on your bench, the only reason to have this guy is for the power up knockout ability with Lava Flow. Since you have to discard energy to use lava flow, I feel Dragonite GX would be a better choice for a heavy hitting knock out. Since to knock out a Reshizard, you'd need to mill 6 energy, or just 3 with Dragonite. Further, I have found the Mach delivery VERY handy in turn 1 a couple times when I wasn't getting the cards I needed to go through my deck. Dragonite is the way to go IMO.
Healing: Solgaleo GX vs Mew3 vs Greninja GX FBL24
These are our primary choices for getting damage off of us. Solgaleo gives us a cheaper option to just remove damage, and comes with an ability to recover energy from the discard which would allow us to need fewer Fire Crystals in play. Greninja has a cool ability which does damage and pulls the whole guy back into our hand, and has a GX bench sniper ability. Lastly, we have the 200 damage full team heal provided by Mew3 itself. Plenty of staying power in this deck. I'll be taking both I think.
Greninja GX PRSM197 vs Altaria GX
Both of these guys have an ability to chew through special defenses similar such as Altaria's Bright tone. Greninja's strength is that he can do it with one rainbow energy, and Altaria needs two rainbow energy. Which puts Altaria as the lead offensive card. However, Altaria has a defensive move for two energy that blocks GX and EX moves which seem to be the majority of the meta, but I am starting to see more non-GX decks. Neither seem absolutely necessary but both add nice utility. If I can only take one, I'd lean towards Greninja for more offensive capability. Especially if we work in Venomoth.
Mew
He sits on your bench and protects the other bench warmers from getting sniped. If your opponent wants to kill him or get around him, they'll have to burn their custom catchers to do it. IMO he is missing from Grant's deck and belongs in yours too.
Defense: Venomoth GX
I won't spend much time on this beyond my personal observations since Krekeler and Manley cover it pretty well in their articles. I personally find the utility of the shinobi mastery a bit swingy, and am considering removing them if I can't find the space to fit them in with my modifications. I will definitely say that it is a nasty mechanic when it comes together. My favorite moment was knocking out a pokemon, and them moving their fully powered reshizard into attack position, and then... nothing. Next turn Dragonite for the win. I totally felt (imagined) their jaw drop to the ground when they realized what happened. Every other match, it doesn't seem to have made or broke my deck.
On to trainers
Janine
If you're not running the venomoth combo, there are better options. Not much more needs said other than she's a better than average consistency card, but there are definitely even better in a vacuum. Such as:
Bill's Analysis
This goes in the deck if you don't run Venomoth. This helps you fish out all the other trainers, stadiums, etc you need, but doesn't really fit in your deck alongside Janine IMO.
+Fire Crystal
If you're running the Solgaleo, you probably only need 1 or 2, because you hopefully won't lose more than a single mew3.
Heat Factory Prism Card vs Veridian Forest
Personally, I have never felt it was a preferential situation to lose a fire energy to draw more. Maybe I haven't been quite desperate enough, but the consistency so far has not made it bad enough. So, I'd not choose Heat Factory normally, however... I'm pretty sure Grant picked Veridian Forest as a way to fish out his psychic energy, and that makes the choice moot since I'm on team Rainbow Energy. The only other stadium cards that are even a potential option is a 4th Giant Hearth or Sky Pillar. Heat Factory it is due to lack of good options.
Switch
I feel like a couple of these were amiss from Krekeler's deck. There have been times I have needed or desperately wanted a switch and didn't have it or even the option of getting it. I'll be adding a couple of these.
Electromagnetic Radar
The only reason to have this in the deck is to fish out Dedenne and use it to more rapidly discard cards to feed your Mew3. With 3 Dedenne, I haven't had issues getting one, and usually end up with a couple at the end that I don't need. Take it if you can fit it, but don't worry too much if you can't.
+Acrobike & +Mysterious Treasure
Both of these feed the consistency engine. If you can't fit them, you can probably do without the extra, but it wouldn't hurt to have them either.
Lastly, Energy
I am fully on board with 4 rainbow energy and 7 Fire energy for 11. I have not ever felt the hurt for energy in Krekeler's deck, and I plan to keep it the same.
So where does that leave us with a post world's deck list? I have 15 cards to play with from what I feel is necessary, and I've smooshed this out.
Pokemon: 18
3 Mewtwo & Mew GX
3 Dedenne GX
1 Venomoth
1 Cobalion GX
1 Latios GX
1 Jirachi GX
1 Reshiram & Charizard GX
1 Naganadel GX
1 Marshadow
1 Mew
1 Dragonite GX
1 Solgoleo GX
1 Greninja GX FBL
1 Greninja PRSM197
Trainers: 31
4 Welder
4 Pokegear 3.0
4 Custom Catcher
4 Janine
3 Cherish Ball
3 Giant Hearth
3 Acro Bike
2 Mysterious Treasure
2 Switch
1 Fire Crystal
1 Heat Factory Prism Card
Energy: 11
7 Fire Energy
4 Rainbow Energy