One of the biggest improvements in my tmux productivity came when I changed my prefix (default Ctrl + b) to backtick (i.e. to `) I am a heavy user of tmux and spend a lot of time switching panes, switching windows, entering visual mode, detatching etc. so this really feels faster.
Backtick is a bit far away, isn't it? I literally have to stretch my left ring finger to hit it, so doing this for each tmux key command does add up I suppose?
I've been using C-z for the prefix for ages. It's conveniently nearly under the default position where my fingers lay and it also masks the mostly useless suspend signal which I seemed to accidentally hit every now and then. (If I really want to suspend my program 'C-z z' will do just fine.)
Switching around using, for example, C-z C-n/C-p is pretty fast to key in. You can keep ctrl down for support and then it reduces down to typing 'zn' / 'zp'. YMMV.