I have a souped-up zsh config that I clone to all my systems, but I've honestly never seen the point in optimizing my terminal emulator. The shell itself provides the real functionality, and it's cross-platform so by leaning on it I get the same features whether I'm on my KDE desktop, MacBook, or SSH'd in via Termux.
What power user features am I missing by ignoring the emulator and focusing on the shell?
You can hold down command and click URLs to open them. (You can actually kinda do this in Terminal.app as well by right-clicking a URL and choosing to open it, but it's a bit fiddlier, and I got used to the hover feedback in iTerm2.)
You can click to highlight entire blocks of output from commands, which I sometimes find handy when things feel like they're blending together.
It'll keep a floating copy of the previous command prompt at the top of the screen so you can see what led to whatever output is currently at the top.
None of these are essential, for sure.
Thinking there are more people who switched out of Terminal diminishes how massive computing is.