> edit: not sure about your mac point. I sometimes use a mac and it works at 200% on two separate 4k screens.
200% scaling works if you only want "looks like 1920x1080", but if you have a 27" 4K display, I'd typically want "looks like 2560x1440" or 150% scaling - if you do that on macOS, the desktop is rendered at 5120x2880 and then downscaled to 3840x2160. So you're getting both higher resource draw from rendering the desktop at a higher resolution and losing pixel-perfect rendering.
It won't be a problem for most people, but it's enough of a problem for me that I won't use macOS with scaled displays.
200% scaling works if you only want "looks like 1920x1080", but if you have a 27" 4K display, I'd typically want "looks like 2560x1440" or 150% scaling - if you do that on macOS, the desktop is rendered at 5120x2880 and then downscaled to 3840x2160. So you're getting both higher resource draw from rendering the desktop at a higher resolution and losing pixel-perfect rendering.
It won't be a problem for most people, but it's enough of a problem for me that I won't use macOS with scaled displays.