My deetz:
Windows 10 Nvidia GTX 970
Latest stable Retroarch, settings:
PSX Beetle Hardware Core
Video Driver -> Vulcan
Core Options:
MSAA 8x
Internal GPU resolution 4-8x
Internal color depth 32 bpp
Adaptive Smoothing
Texture filtering - nearest or SABR
PGXP settings all on, only a couple small places in VS did it cause wacky geometry
Dithering pattern 1x
Crop Overscan
Didn’t need to touch anything else, at least anything with a visible difference. Would have to be at home to check the shader specifics or main system config I ended up with.