How are you resizing when you swap between them without using PIP? Are you just alt- tabbing between a full size instance and several windowed instances? Something you might want to try is making sure your aspect ratios are right on to help with re-rendering. Having a window that is just off a normal ratio does cause some slowdown on rendering. There are sites that can tell you the correct 4:3 or 16:9 ratios for whatever size window you are trying to work with. Just a suggestion.