The DSTWO SNES emulator you want is CATSFC. It's a DSTWO-only emulator because it uses the DSTWO's CPU to improve the emulation.
SnemulDS is for all flashcarts and there is also lolSnes, which is still under active development, but I do not know how well these run. All I know is that CATSFC is the best option out of the three, simply because the DSTWO has more power to emulate.
Also check out TempGBA, the GBA emulator for DSTWO. Some SNES games that were also released on the GBA are recommended to be played on TempGBA instead of CATSFC, because they run better on it.
You can find all the emulators I mentioned here:
The DSTWO uses a Plugin menu by the way that uses .plg files and .nds files.
The .plg files are DSTWO specific programs, like CATSFC and TempGBA.
But you might want to read the DSTWO beginners guide in de Supercard subforum for a more clear example of that and other DSTWO functions.