external display 4K - problem with fonts on scaled resolutions

Hi,

I have external display Benq PD2700U (4K monitor). I connect it (by Thunderbolt 3 -> mini DisplayPot) to my MacBook Pro 16".

It works very well for default resolution for the display (4K resolution, interface looks like FullHD) - text is very crisp and sharp - like on Retina display. But for me on this configuration everything looks too big.

I want to use scaled resolution - but the fonts are not rendered well. Text is not sharp, partialy blury - hard to describe. The fonts are much better on Linux on the same monitor on 3840 x 2160 native resolutions.

Display works quite well on configuration like above, but when I switch it to smaller resolution font rendering goes worse.

What can I do to improve fonts rendering on higher resolutions? Is this issue connected with display, cable, or it is a system bug (I'm on Catalina 10.15.4)? I will be grateful for any help.

Jakub