[kuschku]

The combination of both monitors allows me to check each of my designs both on a high-quality monitor, as e.g. a mac user would have, and on a low-quality monitor.

You probably also have encountered websites which are designed for tiny monitors, and end up with text stretched across 40cm (e.g. HN) or websites with razor-thin text that is basically unreadable on cheaper monitors.

As I work in UI/UX design, I want to avoid that issue :)

[nitrogen]

designed for tiny monitors,

Or designed for non-maximized windows. It gets pretty frustrating when sites serve me a mobile version just because my window isn't 3000 pixels wide.

[vdfs]

KScreen is weird, i had a scaling issue that happen if at boot, both my 21"+27" are connected (they are both FHD), but if i boot with 27" monitor then after login connect 21" there is no scaling issue. Maybe that could help you somehow You can also try to put your PC in Sleep instead of restart each time, if you have a good UPS and some redundancy