First of all it fixes for any color, giving it a lot of flexibility, but it also transforms into a sizable 5/5, which can be key for the middle of your game, or act as a life saving chump blocker closer to the end
All of them are the same card mechanically, but feature different art with new suits
Tucking a cheap creature early makes it much less relevant when recast later, or you can use this in coordination with a counterspell to deal with the threat for good
Im most inclined to suggest a Voltron playstyle for Kefka, since both halves benefit from combat buffs, but honestly, you can build any deck around him
When not in use, store your top loaders in a cool, dry place
Spells, activated abilities, and triggered abilities can't raise its power in time to change the value of X