Just some thoughts:
Because of the nature of modern displays vs older crt tvs, retro games can often feel a bit laggy on modern displays re: input delay.
Most modern emulators have a way of getting around this, for example https://docs.libretro.com/guides/runahead/
You'll also want to enable your display's "gaming mode" which helps by disabling unnecessary image processing/"enhancements".
@scheisse_poster Within Retroarch, I just set runahead by 1 frame & second instance mode by default.
edit: for 16 bit systems I also use the bandlimit-pixel shader by default (a simple interpolation filter that smooths out uneven pixels caused by upscaling). Something else to look into :P
@scheisse_poster I did that, then came out the other side and just ended up saying, eff it, bandlimit pixel for simple interpolation and that's it, lol.
The shader hole can become an obsession.