I use NullDC for dreamcast, Makaron for Naomi, & Demul for Atomiswave/Light Gun games.

The last few Makaron builds were pretty glitchy from the author experimenting with different things.
I use version T12/5 and it plays the NAOMI arcade version of MvC2 fine.
I remember a patch being needed to get MvC2 working on one version, then not being needed in the next.
Not sure which version that was.

Google "MvC2 Makaron" and you'll find tutorials.
Don't remember the specifics, but the game didn't work as well with Demul.
I tried MK Gold on NullDC and it ran slow on my system.
-didn't try it on the other emulators.