Most recent build of CATSFC is a pretty sizable improvement from the official NDSSFC emulator that the Supercard team left for the DStwo. Though a lot of those improvements come with the added cost of some battery drain, since it defaults the emulator to run the DStwo's chip at its fastest speed. Still, it helps a lot. SNES games that didn't require an extra chip in them to boot/process are pretty much a given on the card. Between it and SnemulDS, there aren't many such games that can't be run well.
Though again, things change when you start involving games that did have additional chips on the cartridge, such as the DSP chips for the MegaMan X games, or the compression chips a lot of RPGs used to fit on the available amount of ROM chips they were able to have on the cartridge. For those games that used compression chips, I understand there's a way around that by de-compressing the rom somehow. It balloons the size of the game, but it renders the need to emulate said compression chip pointless.
As for the GBA, unless you have a DS lite, your only real choice is going to be the DStwo's emulator. Not perfect by any means, but it is serviceable.