I usually prefer 2x scaling on a 4k screen, and then pictures and text are unscaled. I like being able to put a 1080p movie in the upper left corner and a reference webpage below that, then a big text editor to the right and 'work'.
Why would you be looking up and down?
I just find it simpler to have 1 high resolution screen where I can put high def content side-by-side or in quarters on screen.
For now this works, but in 10 years when movies and web pages are 4k by default I'll need an 8k laptop screen (haha)
(Probably at 17" though)
When I am working I only use one screen, and only one window in the screen, and instead I constantly switch between virtual desktops, to the point where I just think "browser", "editor", "terminal" without even perceiving the keystrokes.
However, for gaming I dream of having one of these ultrawide screens that have the resolution of 3 normal screens side by side. Something quite complicated to have in a laptop, but I have seen some attempts.