OK, not much I can see, but I guess that you are redrawing your whole editor all the time.This is much worse on Windows as on macOS as macOS throttles redraws to 60 or 30Hz, while Windows does not do this. Another thing you should do is eliminate every offscreen buffer you have introduced yourself to reduce flicker in VSTGUI3.6. This is not necessary any more and handled by VSTGUI itself. You need a profiler to see what is going on.
Cheers
Arne