I use a 1080p monitor and what I’ve noticed is that once creators start uploading 4k content the 1080p version that I watch on fullscreen has more artifacting than when they only uploaded in 1080p.
Did you notice that as well?
Watching in 1440p on a 1080p monitor results in a much better image, to the detriment of theoretically less sharper image and a lot higher CPU usage.
The one I’ve noticed is that for videos with the 1080p “Enhanced Bitrate” option, the free 1080p video looks like a blurry mess compared to normal 1080p content.