It's definitely not a gamble. When you press Cmd-Tab, first of all, if you hold it down for longer than about a second, it shows you the icons of the currently

It's definitely not a gamble. When you press Cmd-Tab, first of all, if you hold it down for longer than about a second, it shows you the icons of the currently-open applications, letting you select which application you switch to. Whenever you use Cmd-Tab to switch to an open application, it will always foreground all the open windows of that application that are on the active desktop/space. When I'm doing something like you describe, where I know I'll be switching back and forth between a specific pair of windows of different applications (and I have a bunch of other windows of those applications open), my usual practice is either to size and position them where I can just see both at the same time (large screens ftw), or I'll pull them off into a separate space where Cmd-Tabbing between the two applications will be guaranteed to switch between just those two windows.