@lendário Hum ... I'm definitely not in the shader sutff.
What I can say is that, depending on the shaders, it can be CPU intensive. That's why we recommend 720p : that's just for a performance issue.
Regarding the ratio ... That's again a different story. This all depends if you want plain square pixels, or if you want to emulate the 4:3 stretching done by TV. There is much to argue about that ... Once again, not the kind of thing that matters when I play.
Integer scale is something interesting but "looks best" on 1280x1024 as it's the resolution that is the closest to integer multiples of original resolutions without having too much black borders. When you don't use integer scale, you need bilinear filtering to avoid some graphical issues.
I'm not of much help here, i don't have the same goal when playing 😉