I've been using Xfce on hidpi since 2015 with just font scaling (using the DPI setting in xfce4 settings/Xorg), and it has worked fine, other than the minor issue of unscaled icons in the Window Buttons panel.

Yep, but they are all high quality. Xfce has been my daily driver for over 10 years now. I've just had to wait patiently to buy HiDPI hardware - and now it's cheaper so for me win/win