[emu]

Yes, the difference between 4k and 8k text is easily noticeable for a 32" monitor, and I'm not particularly eagle-eyed. Text is sharper and finer details are better rendered. For videos and images I don't notice the difference in practice.

I had a 4k 32" monitor at work and found that it simply didn't give sharp, high resolution text, driven by either a Macbook or by a Linux box. And you wouldn't really expect that, either: a 4k 32" monitor is only ~140dpi, which is only marginally higher resolution than the ~100dpi screens we had for many years.

I think the best point of comparison for the Dell UP3218k monitor which I have is a Retina Macbook Pro screen: subjectively, it's a similar experience in terms of text sharpness and legibility (>200 DPI, glossy), just in a 32" form factor.

I suspect 8k at 32" is actually a bit higher resolution than necessary (~280dpi), but there's nothing else on the >30" high resolution monitor market other than Apple's 6k display, which is significantly more expensive.

Be aware that there's no Mac OS support for 8k displays, but Linux and Windows on a desktop with a reasonably modern NVidia GPU work great.