As I am currently developing in a Win7 Parallels 11 VM (1920x1080) I have my entire window design in one view. (2015R4.1) . I also have a Win10 VM running, and shown perfectly fine, no problems with any program, but Xojo IDE.
The picture below shows left Win7 2015R4.1 IDE and right Win10 2016R1 B13 IDE. Mind that my formdesign gets blown up (or zoomed in if you like). 
Other parts of the IDE are shown something different but that’s ok. The Windows 10 text-size is set to 100%.
I heard that it could be related to Parallels VM, which is hard to believe since the whole bunch of other applications is shown perfectly fine. Does anybody have the clue ?
It looks as if Windows 7 is displayed at a higher resolution.
I double-checked, same resolution. (1920x1080 on both)
I forgot to remark that when I build or run my project in debugmode, it’s shown as expected, no issues. It’s just the IDE. I checked with 2015R3.1, and had the same, so that’s why I did not post this in the B13 chapter.
Joost, what do you see if you go to Settings / System / Display / Advanced Display Settings? It sounds like the scaling mode is wrong.
Are you by chance using this as a VM under VMWare Fusion? I’ve seen it muck up the scaling settings.
I’ve double checked every one of my VM’s to make sure I was not getting oddities and all mine look fine from Windows 7 thru 10.
And I’m sure we’d get pummelled by Windows users if it weren’t - and we’re not.
This leads me to suspect your VM is playing tricks on you