I don't know if this is something you can change within MB or not, but I figured I'd mention it.
With the old "XP style" magnification, MB is fine in Windows 10 because all screens are magnified at the same ratio (125%/120DPI). However, I switched over to the default scaling method found in Settings > Display because I have some apps (less well-supported than MB!) which are unusable with the other method. In this method, my main screen is scaled at 125% and my external monitor at 100%.
The trouble is that then MB looks fine on the 125% screen, but all the text and icons are blurry on the other because it's trying to use the same scaling.
Update: nevermind. Turning off DPI scaling for MusicBee3.exe solved the problem.