Personally I don't like retroarch and prefer standalone emulators. Here are some emulators I use regularly:
pemu: includes standalone nes, snes, arcade (final burn neo) and genesis emulators.
mgba: gb/gbc/gba emulator
Emulators with performance issues:
ppsspp: performance is a hit or miss, can't handle some games at high res. Latest build I can find is pretty old.
melonds: performance issues in some 3d games, ok for 2d games
For ps1/psp/dreamcast/ds/3ds emulators, you might as well use the android version.
And my favorite ports:
revc/re3: reverse engineered gta vc/3 ported to switch. Original github repo is down but not hard to track down a copy. Much better than the definitive edition
sm64 switch port.