Got my cables in recently so I’m happy to finally write this report.
On default OSSC settings, only x2 works.
However, with adjustments, I could get x3 and x4 working. Adjust V. active to 256 and V backporch to 3 and an image appears. SNES requires backporch adjustment to 2. It leaves a blank space at the top with those adjustments however. The TV reports the output as 1280×768 for x3 and 1280×1024 for x4.
There is no sound in x4 mode, however there is sound in the x4 320×240 optimized mode.
x5 does not work, even with the adjustments suggested in the relevant thread.
Super Famicom works, tested with a 1CHIP-03 system with a sync on luma cable. However it only works in the generic modes. 256×240 optimized mode results only in flashes of an image at regular intervals, but nothing more. Probably related to the uneven sync it outputs as outlined by Marqs. SNES is the only 256×240 console I have to test this mode.
480p x2 works, with adjustments. Need to set 480p sampling to VESA, and then adjust V. active to 512, and V. backporch to 11. It leaves a blank space up top just as the 240p x3 and x4 modes with adjustments.
Unfortunately you can only zoom in or change image position in 480p output, when outputting any of the higher resolutions the only options you have are 4:3 or 16:9 aspect ratio change.
480i x4 does not work (nor x3). It should output the same resolution as 480p x2, or so I thought, but I can not get it to work.
Sega Saturn (Japanese model 1)
GameCube (NTSC) (480p and 240p via component)