I only played one Jigglypuff, but when it comes to winning you want to use the heat seeking missiles, Zair is good since she's in the air almost all the time, and keep yourself from getting hit by a lot of aerials. Knowing where and what jump Jigglypuff will land on. Killing shouldn't be too hard if you punish Jigglypuff's landings correctly. Jigglypuff is obviously going to try gimping you any chance possible. Our ground game is better than Jigglypuff's, but Jigglypuff's aerial game is definitely a lot better. She can cancel out missiles with a few aerials. Her main kill move would be fair. Samus of course is going to have some trouble being up close as always.
Stages to CP I would pick either Halberd or PS1.
Stages to ban is Brinstar/RC (if they are legal), not sure what else to ban.
I would say slight advantage or even.
Sorry if I'm not too good/knowledgeable yet, but this is my input.