I have recently been working where I have around 5 windows open. Editor, Terminal, Documentation, Email, Browser with test profile.

I've found that alt-tab hasn't been working the best for me, but what has worked is having mostly overlapping windows, with a bit sticking out that I can click on to pull it to the foreground. Maybe I should be assigning some keyboard shortcuts to pull up particular windows, but this works reasonably well, and is easy enough to adjust if I added a 6th window, or whatever.