Ok, here are my findings:
Newest stable (hotfix) RetroNX, using pre-configured PCSX Rearmed config, FAT32 SD card. Settings are as follows...
-16:9
-Integer Scaling disabled
-Sound interpolation disabled
Resident Evil Director's Cut:
Video: Some graphics glitches. Examples: Selector Box in inventory missing lower part, first zombie encountered has no right arm. 59.3-60.4 FPS.
Audio: Some audio stutters. Example: during dialogue, there's a stutter every half-second. Worse during cutscenes. Watching the beginning video was awful. Using "switch_thread" or "switch" for audio driver makes no difference.
Skullmonkeys:
Video: Flawless. Solid 60 FPS with no graphics glitches.
Audio: Same issue as RE: DC.
Kurushi Final/Intelligent Qube:
Video: PERRRRRRRRFECT!!!
Audio: PERRRRRRRRFECT!!!
Final Fantasy IX:
Video: Runs great, even during FMV's. Some minor glitches, but I don't remember if those were in the original or not. Will compare with my disc/PSX. 60 FPS.
Audio: Same issue as RE: DC. Worse during FMV's.
Tony Hawk's Pro Skateboarder:
Video: Great! 60 FPS.
Audio: Same issue as RE: DC. Mute it, because it's awful hearing music like this. Sound effects do not seem to be affected.
Vigilante 8: Unplayable. Crashes RetroNX.
Video: Cannot test, crashes RetroNX.
Audio: Cannot test, crashes RetroNX.
Tomb Raider: Unplayable. Crashes RetroNX.
Video: Cannot test, crashes RetroNX.
Audio: Cannot test, crashes RetroNX.
So yeah, those are my findings. I'll continue testing games that others haven't reported and post my findings.