i use linux on a retina macbook @ 2880x1800 and fractional scaling works well in swaywm. they warn against it in the docs, but no problems so far (though it's only been a week)
right around QHD is the sweet spot imo. I use 3 30" Apple Cinema HD Displays @ 2560x1600 (my school was throwing them out), and theyre perfect for everything. games, code, movies, whatever. Needs dual link dvi though, so old gpus only.
My grandmother used to have difficulty reading her email, even with double font size, low res, etc. Over the summer, I replaced her monitor with a 32-inch 1080p TV that I had lying around, and it makes a big difference.