Hi,
first of all, you have to setup your bitmaps as I described to you here: Supporting HiDPI programmatically (no UIDescription) - VSTGUI - Steinberg Forums.
Next, if you do not use the VST3Editor class, you have to set the CFrame scale factor yourself, by listening to calls to IPlugViewContentScaleSupport::setContentScaleFactor (…).
By the way, way are you not using the VST3Editor class with its WYSIWYG editor ?
Cheers,
Arne