For me, ideal pixel density is when I can draw a 45 degree line with high contrast, eg white on black, and there are no blocky pixels visible. No stepping at al

For me, ideal pixel density is when I can draw a 45 degree line with high contrast, eg white on black, and there are no blocky pixels visible. No stepping at all. Even better is the density where pixels effectively disappear altogether. Same for any other angle. Aspect ratio also matters. I should be able to take a square and rotate it and it shouldn't change shape. Measurable using a physical ruler for best results. It doesn't sound like a big deal until you rely on it. I'm sure theres a research paper about this effect contributing to fatigue. Refresh rate and lighting are also important factors. 60hz was a gimmick for me until I got a setup that could maintain it. Originally I figured it was no big deal but now I actually notice when I use a lesser setup of monitor and computer. Its a different experience. Its not a sense of "this is wrong", more like "this isn’t as snappy". Not as responsive. At around 40", I find 4K on a monitor is "fine" but there can still be some stepping. At lower screen sizes, 4k for me is "excellent". I think 8K or similar at 43" would achieve the "no jaggies whatsoever". Maybe even less pixels would suffice. BTW I'm not talking about setups where you sit away from screen like a TV watched from a couch.