Here are some more examples. And I dont know why, but it looks a bit better in game. I don't know why some of the quality is lost.

Here you can see that small text is still readable









Here is my custom preset for the Retroarch shader.
https://ufile.io/08loeSomething is wierd with my ReShade and I can not share any config. But I will tell you what to set.
First is effect ordering, this is important.
High Pass Sharpening -> Vibrance -> Deband
High Pass Sharpening values -
1.0
2
0.80
1
1.69
1.0
1.0
0.00
0.00
0
Vibrance values -
0.30
1.00
1.00
1.00
Deband values -
18.0
0.100
8
3
3
0
1.0
0.0
Remember that after this, you also have to make Retroarch run in fullscreen 4k resolution. And the internal resolution should be 2x to get the best out of the pre-rendered backgrounds.