Yup, it's 6 buttons that you can map. As for the balance, I only played with Ken, Ryu, Cammy, and Chun-Li. Chun-Li's moves have shortened lag time, so enemies can't punish you as much...she is weaker though.
As for Cammy, many of her moves push her away from the enemy when blocked and a few moves have invincibility for a brief time so she won't get punished. Like for example if someone blocks your Cannon Spike, you have a little period when you come back down that you can't be touched...but that could be a bad thing.
Also, Cammy has been returned to a "power" character, her moves do a lot of damage. She got stronger while Chun-Li got weaker punches.
