Tile sessions in a terminal with custom setups for each tile
I used tmuxinator and byobu for this. Tmuxinator allows you to start one or more sessions of tmux or byobu (programs that gives you virtual terminals) and for example tile them.
It was hard to predefine setup commands in tmux or byobu directly, but with tmuxinator you can do it in a YAML file. I believe it uses sendkeys instead of relying on tmux' command parameter.
Manage complex tmux sessions easily
(for any nitpicker reading this, I mean what is referred to as panes in tmux and byobu when I write sessions.)