As these things normally go, I just found a workaround right after starting this thread:
I'll see if your workaround works ;-)
Other thing to check:
I just found another work around which is much better:
http://www.danantonielli.com/adobe-app-scaling-on-high-dpi-displays-fix/
This results in everything working fine as it should on my system now. Except for the Mendix Modeler, which is rendered on fhd and scaled by windows to qhd. This is obviously still not perfect, but at least it's usable.
Since my original post I have gotten convinced that in fact the Modeler is the problem, as (on my system, and I don't use any Adobe software other than Brackets) it is the only application not scaling correctly.