(Here we go...)

I'm curious what your essential configurations are. I've been using default tmux for years, am I missing out?

Personally the only thing I really need is `mode-keys vi`, the rest is optional. I guess you want to configure mouse on/off depending on preference, if it differs from the default.

Usually will at least change the color of workstations and desktops just to make it more visually obvious which tmux environment I'm looking at when sshing and nesting.

I remap the escape key away from C-a as that conflicts with emacs and I increase the scrollback size of sessions.

It's C-b by default, C-a is what screen uses. Maybe you copied someone's config, as that remapping is fairly common (or weird distro default? but seems unlikely). I'm personally fine with the default C-b and have always kept it everywhere.