BSNES core is not implemented yet on the RPi (I dont see the option to install the core in RetroPie Setup), the only snes emulators inside retroarch are the following:
…but maybe something was updated, I’m going to check this. Btw, even if BSNES could be implemented in retropie dont expect full 100% speed, not even half of it, BSNES requires a high end PC to run in accuracy mode, I doubt the Pi can handle it right now.
I tried the bsnes core in retropie (manually added it myself) it was was unusably slow. So slow I wouldn’t even call it functional. I’ve heard that bsnes is the most processor intensive snes emulator so it might be unrealistic to expect it will ever run well on the current pi hardware.