Just downloaded this and gave it a try. Worked with no issues.
So what does it do? This loads a bunch of filters that can be applied to the game and allows graphic settings adjustments not in the original game.
For one example, you can enable SMAA.
It also gives ultimate control over many settings. You can adjust either FXAA or SMAA in ways no video card will allow.
You can change gamma, exposure saturation and other settings with the tone map filter.
Has some fun filters for looks that I wouldn't use to play the game, but would make interesting screen shots.
I've just been playing with it, but the default filter list includes well over 30 filters. You just select the ones you want to apply and leave the others deactivated.
Basically, it gives you as many effects and filters to play with as an advanced video editor does, but these are applied to your game.
Presets can be saved and shared. You install it for each game, so using it on SH4 will not affect any other game.
It also has a raytracing plugin that works with it I obviously haven't tried yet.
Will post more info with screenshots later, but wanted to give a heads up. If you are interested, it's available here.
https://reshade.me/