copy "psnes" directory to "/switch/" directory on sdcard
copy roms to "/switch/psnes/roms/" directory on sdcard
pSNES actually support save states, 2x, 3x, fit, fit 4/3 and fullscreen hardware linear scaling and a simple (but nice?) ui.
pSNES ui support titles images (png), named as the rom name with png extension instead zip, in the "previews" directory (to be created if needed).
pSNES does not actually support high resolution games...
pSNES use a database file for rom handling. You'll need a "db.xml" file located alongside the application. The current "db.xml" file comes from "Hyperspin" website, and only contains USA "good rom / no-intro" set. Your rom files must be zipped and named as per this set. You'll find in the "database" directory this file as backup/reference (Super Nintendo Entertainment System - hyperspin.xml) + a complete set from dat-o-matic ( Rename this file to "db.xml" and (re)place it in the same directory as the executable to use this one. You can make your own database file with filtering from this great website.