Any settings you want, Duckstation can pretty much run on a potato, just maybe don't go to high with the rendering resolution, there's not much point in rendering ps1 games past 1080p.
PS1 games ain't gonna look any better at 4k or 8k.
Other enhancements are up to preference, like if you want to use any filter or dithering etc.
Enhancement that you should leave at default unless you know what you're doing are.
CD speed up and seek speed up.
PGXP depth buffer and CPU mode
These can improve games but also break them.