Hi there,
Regarding your last inquiries, have you tried using the "Ctrl+ +" and the "Ctrl+ -" shortcuts to zoom in/out?
Additionally, you can enable the "Adjust render resolution to VFB" option if you're using the IR; by doing this, resizing the VFB window while running the IR will adjust the image size to the VFB size. (see attached screenshot)
I hope this helps.
Cheers!