PalkiaChomp is by far the best variant you can use. I got 5th at States with it, even winning against a couple LuxChomps outright along the way. In fact, it's one of the few decks to have even footing with LuxChomp. It does have a couple issues that you might want to think about before using it.
1. You have to get prizes early, or you will struggle.
2. There is no room for a Mewtwo counter. Period. No, seriously, the list is too tight for one.
3. Luxray. Okay yeah, the deck has even footing with LuxChomp. But that is only because you have to run Promocroak and keep them under a spray lock so they can't heal breath or bright look.
It really is the only SP deck I will truly reccomend, it's a blast to play and it actually can win quite a few games. Machamp might do some damage to it nowadays, so keep an eye out for that too.
EDIT: I just want to clarify and say that PalkiaChomp is arguably the best variant. Legos might have a bit of fun this format, but I don't know personally. I just know that I went 4-2 in Swiss at States using PalkiaChomp, and would have probably done similar at Regs had I not goofed my 5th round match...stupid 3-1 record went downhill after that.