I've made a couple of posts in
this thread that you may find helpful. It talks about cards up to Primal Clash iirc, but the concepts should be up to date, unless they are really fast and require Lysandre's Trump Card, a card recently banned.
But yeah, I've classed 4 main types of decks that perform at 3 different speeds:
Consistency - Really consistent. Often uses 4 of many cards and likes to use cards that help get more cards. It is very good at getting the card you want when you want.
Speed - Fast/Aggressive. You want to dish out damage as quickly as possible (and take prizes as quickly as possible), and you aren't afraid to lose some resources doing so.
Disruption - Disrupt (aka annoys) your opponent from playing his deck. Discarding energy, switching your opponent around, changing hand sizes, prevent attacking, prevent the use of items, etc are all types of disruption.
Support - Quite tech based. Often has a lot of answers to a lot of decks, although may require sacrificing a bit of consistency to do so.
Fast - You draw through your deck quite quickly and start doing heavy damage early, although a quite reliant on items and/or abilities, not an ideal deck against the popular Seismitoad-EX and Garbodor decks. This type of deck is somewhat unviable as it is quite easy to deck yourself out (have no cards in your deck at the start of your next turn), which leads to a lose for you. Lysandre's Trump Card was once available to remedy this, but has since been banned.
Medium - Your average speed of deck. You take perhaps a couple turns to set up but are difficult to stop while in moving along the tracks.
Slow - Slower than normal, generally because the Pokemon have pretty heavy energy costs. These are mostly unviable as any deck of a faster speed can generally overun it, especially using Lysandres to destroy any being set up on the benched.
The linked posts I gave you go into a bit more depth, so worth a read if you are yet to.
