Now why oh why didn't I listen to my head and NOT take your advice? I followed the purge instructions exactly, and even made manual backups of the stardock user folder and registry key, reinstalled and it's a MESS. It has retained my fences (& no longer brings up the option screen on startup), but...I'm now on 2.13 when I was on 3 before, the settings-window's font is miniscule at 4k, and I can barely distinguish the individual snapshot images:
https://i.imgur.com/hJLOOh4.png
and the icons on my 2nd (1920*1080) monitor are spaced massively apart:
https://i.imgur.com/Arm4Orv.png
(the icons on the left are not in a fence, the centre-screen icons are all in one fence):
https://i.imgur.com/oz5vPgH.png
note the huge gap between non-fenced icons on the left (next to my vertical taskbar). I should have known better than to EVER consider a "purge" as a solution to a minor issue