Both screens are set to 100% scaling, however my playfield runs 4xDSR full time, so this is likely what's causing the issues. I bet if I was running native 4K everything would look uniform. I tried all your suggestions but in my case they made little difference (unmaximized screenshot attached).
I remember a short while ago the font sizes were all out of whack after some update, but you guys managed to fix it in subsequent releases. I get why this may not be possible going forward for non-standard users like myself, since you've enhanced window sizing capability and that's more important anyway. It's no big deal, just a cosmetic issue that I can live with. I very much appreciate the continuous improvements to the software, and I can honestly say your DBX Manager is the reason I have kept Pinball X as my frontend.