I didn't mention HDMI (Or I don't think I did) although most desktop PC users and gamers will indeed be using that, as most cheap (and some expensive) monitors and TV screens do.
For still-photography purposes most digital Video connection standards are ok. The graphics cards can load some surprisingly different defaults for Display Port , DVI and HDMI but you can work through the card settings and get to the same place.
It sounds as if your eyesight may be another factor and I'm no expert there. I would imagine though that if things look different between screens, screenshots and postings then there is a non eyesight problem to deal with first. After that is done any adjustment to the monitor settings that help you should help with all images and not just some.
HTH