I have a Sony XBR55X900E and the latest OSSC 1.6 w/latest firmware. PS1 worked in 3x, 5x (and I think 4x) modes. PS2 worked in a few of the modes as well.
SNES only worked in 5x with 256×240 optimized, but the picture is not stable (will drop every few seconds). It was even less stable in the “Generic 4:3” mode (might flash an image every few seconds). I’ve played around with some of the settings as per the wiki page. I’m not sure if any additional tweaks will help or not. I’ve tried some of @Harrumph’s Tips and Tweaks earlier for 5x to no real avail. I may try some of the 3x/4x tweaks at some point in the future and hope it’ll work. It’s one of my favorite systems ever and I opted for the OSSC over the SNES Classic in hopes I could breathe new life into my SNES.