BTW, the answer to the question 'are overlapping windows bad' is . . . . . . maybe.

It really depends on the idiosyncrasies of your hardware and software working together. For some people it can be.

It's obviously pretty simple for you to test yourself if you see any performance difference with overlapping versus non-overlapping windows. That's what I'd recommend. This forum is a fantastic resource for experiences and suggestions, but yes/no answers ... not so much. Way to much variability in everyone's setup.