no trouble with the theme.
As you can see on this commented capture, the fonts in FARR are not high DPI aware ("not retina")
You can see the difference (4 times more pixels...) between the FARR windows Title (drawn by windows 10) and the result list.
On the capture, behind FARR, you can see Directory Opus, which is now fully high dpi aware (since dopus 12)see dopus doc [Feature request] FARR retina (high-dpi) aware ?
Having a fully high-DPI aware application does not come that easy, i know FARR is THE best software in the universe but nonetheless mouser will have some work to do