Funny you should mention emacs, I use emacs as well in a single frame-per-buffer setting. While this used to be a mess in older times, modern GUIs like Gnome and MacOSX allow for better navigation with Alt/command-Tab between only the programs and Alt/Command-` between the windows of the same program. And as usual, the Window manager is the best tool around for managing windows.
I never got the fascination with splitting terminals full screen. I simply open as many as I need and let them cascade. If, by chance, I need them side by side, I can always drag them. There's never a real need to have all the terminals in a single window, as we are, sadly, only able to focus on a single element with our eyes. So while technology allows us to fill the screen with information, biology dictates that you don't really see it.
Also, screen and Tmux are much more than just for splitting a terminal, they are a relic of a time where all you had was one window and one terminal and the only way to access multiple processes was with a multiplexer. These days, well, we don't need this. There are valid uses for screen/tmux of course, but less on the display side, unless you are running without X in a frame buffer environment.
Funny you should mention emacs, I use emacs as well in a single frame-per-buffer setting. While this used to be a mess in older times, modern GUIs like Gnome and MacOSX allow for better navigation with Alt/command-Tab between only the programs and Alt/Command-` between the windows of the same program. And as usual, the Window manager is the best tool around for managing windows.