`set -g mouse on` should be all that's necessary to enable mouse-wheel scrolling for tmux version 2.1 and up. This works for me.
https://superuser.com/questions/209437/how-do-i-scroll-in-tm...
https://superuser.com/questions/209437/how-do-i-scroll-in-tm...
I’m pretty new to using tmux as more than a basic screen replacement, but it seems flexible enough that almost anything you want can be configured.