ok at least for me I've found these are the best emulators for each game type. This is just imo, but I don't like demul or nulldc for naomi games.
Nulldc => Dreamcast
Makaron => Naomi (pretty confusing to configure keys)
Demul => Atomiswave
There is actually a special version of demul out there that just focuses on emulating atomiswave, I can't link you because they also host the roms
For me the advice I can give you based on my experience...
1. For nulldc I had to install Visual C++ 2010 Runtimes (available on their google page), i used the same bios I was using on the older nulldc and it worked like a champ
2. Make sure your bios are named correctly (they all use differently named bios)
3. Make sure your games are in the format that works with atomiswave and makaron. I think both run mame roms now, but Makaron can run .dat format roms.
4. I guess it wouldn't hurt to make sure you have the latest direct x