You are granted immunity to the special action you don't pick. Gamma's dash action + Rouge's dash attack is amazing. Even if you unlock the ultimate bomb technique, this one is far superior. There is something very wrong with Cream's Aerial bomb technique, which despite supposedly being a fast and weak move will 2HKO every character in the game. You'll never use guard, ever, so you want to minimise the time spent guarding before you start healing. Rouge's guard is rated the lowest and is also the least costly, but its actually the best. Unfortunately, the cooler stances (CHAOS!) are really slow.
Stance looks like its purely ascetic, but it changes the speed at which Emerl can turn around, and also unlocks Gamma's fricking self-destruct attack and I think Shadow's teleport chase thing. I've no idea how you're getting all those colour change cards though, aren't they supposed to be insanely rare? Unfortunately the mechanics aren't that good, and the sound font hasn't aged well but still, fond memories. Hell yes, this game was awesome when I was younger.