I have isolated these games that are not listed by FBA in my GCW Zero. Aren't they supported or is it that they are not correctly named or belong to a wrong version?
Finally, another question: does selecting a different emu core help with performance or is it only useful in case a game doesn't work. It has helped me with the latter case but not the former. I have tested several games which don't reach 60/60 and the results do not differ.
Please, before trying any games, consult the supported gamelist: https://www.sendspace.com/file/tuooid
Btw, the link is in the first post. If the game is not there (rom name without .zip), then the game is not supported.
As for the cores:
a68k is written in mips assembler. It was a challenge for me to make it work right, the original one was written for psp (and its firmware has a slightly different architecture than OD). In fact there was not much sense in fixing it since the performance is roughly equal to c68k.
c68k is the fastest portable core but it supports 68000 processor without protection. It was dropped long ago in some old FBA version, but I brought it back.
m68k (Musashi) supports 68000 with protection and its derivatives: 68008, 68010, 68020, 68EC020 and 68040. It's the most feature-rich and stable core, but not so fast.