Nope, theres no issues with certain video modes, it's just you doing something wrong.

That screen shoot looks more or less normal, standard 4:3 proportion, just like PS1 games were made, since you know back in the day we old folk didn't have non of that HD or wide-screen gimmicks.

So if you want to stretch the screen then simply turn off "keep PSX aspect ratio" or set "stretching mode" to 0 depending on which plugin you're using.

 

I have tried using that option as well as the widescreen fix (while setting a window resolution that is a multiple of 640x480).

I've attached three more screenshots to clarify.

Battle Arena Toshinden compressed horizontally

Ridge Racer Turbo Mode loading screen

Ridge Racer Turbo Mode main menu (it looks to have switched to a different video mode at this point. I'm assuming this is the 60 fps mode here).

Note how the stars fill the entire window in the loading screenshot yet the screen is small, surrounded by black space in the following shot. It looks the same in windowed for fullscreen.

 

Well by looking at these SS i can tel you're still have on either "Keep PSX aspect ratio" or other stretching mode then 0.

So unless you turn that off nothing else can be done.

 

Thanks for pointing me in the right direction, Fox.

I fixed the issue by turning stretching mode to 0 (stretch to full window size), setting the windowed resolution to 1440x1080 and turning on Use Window size in Fullscreen mode (Widescreen fix) then running in Fullscreen mode.

I don't understand why the plugin isn't smart enough to simply scale the game to the constraints of the selected fullscreen resolution while maintaining the Playstations aspect ratio. Every other emulator does this: MAME, Higan (bsnes), SSF etc. Or maybe I'm just not smart enough. Yeah. It's probably the latter.