from memory my laptop has Xft.dpi: 144 set in ~/.Xresources which corrects most programs I use for the 3200x1800 13" laptop I have. I think I messed with qt scaling somewhere but I can not remember where I did that as it was a while ago. The Arch Wiki link is a brilliant starting point.
I recently posted a thread for Endeavour OS i3wm, which is also an Arch based distro. Perhaps some of these settings will help you too! It took me a while to fix things on high dpi screen.