3. again, forgot to mention of course the 1920×1080 mode will be wide since it crops the image to display 1536×1080 area = 1.42. Dunno what’s up with your 1920×1200 mode though, probably some scaling on your TV.
In relation to what paulb_nl wrote, you can basically set H Active to anything that works for your monitor, most seem to ignore this value for scaling/AR adjustment anyway (so it wouldn’t affect the scaling of NES/SNES games anyway), and 1600 is perhaps especially appropriate for 1200 height mode.
Regarding your PS1, I don’t remember but might be one of those where you need to adjust the sample rate up or down by one (because dot clock is not exactly 341, just close). Alternatively, adjusting video LPF could probably help. Really doubt sync LPF would have any effect at all.