Thanks @OttoKerner . Windows Explorer > Right click Plex icon > Properties > Compatibility - Change high-DPI settings > Overwrite behaviour with high DPI scaling > Scaling performed by: > System
Does seem to work - I may test Plex more sometime.
Still, this is something that should be fixed in the Plex app itself, instead of expecting every Windows user to go through these steps. I hope Plex fixes it someday with a code change.
