The Pokmon fusion generator is my favorite tool for making new Pokmon creatures
Every Card
If they're playing a tribal deck, that 1/1 will count as whatever creature type they're playing, because it has changeling, meaning it's every creature type
The stats are solid on this one, even if its not flashy
Decks from any format (e.g., Standard, Expanded, etc.) can be played, but note that success in the game is based on overall damage output, so you may deal more damage, and thus have more success with newer cards (i.e., Sword and Shield onwards)
Skypiea has deep emotional resonance across both Japanese and international fanbases, and Enels villain status gives him a collector profile that doesnt depend on competitive play relevance