retropie supports neither mugen nor the switch, so...

Wine only emulates the operating system, the PC Diablo binaries are still x86 so will never run on a Pi. If you want to play Diablo, there is a PSX port. Yes, N64 emulation is crap for many games, the Pi is weak and emulation is not that good anyway. A few games work well such as F-Zero X. There are apparently some improvements to N64 emulators coming so maybe the situation will get better in the next few months or year.