Tried playing with the panel icons size. Entire desktop is scaled “2x” under Settings.
Struggling with GTK3 + GTK2 synergy under XFCE 4.14. (Please halp!)
I don’t know if this is related to your problem but maybe it helps:
https://wiki.archlinux.org/index.php/HiDPI#GUI_toolkits
I mean the GDK3 (GTK3) part. 
The XFCE section is outdated. When I first found out XFCE 4.14 would have HIDPI support I was under the impression it’d manage all elements like KDE.
HIDPI support in XFCE 4.14 feels incomplete.
Thank you anyways, I’ll come around to this again. A kernel bug’s been defeating my experience across distributions. Can’t even begin to troubleshoot it.
Sorry for the rant.