Long-time (25+ years) Emacs user. The first thing I do on a new installation is turn off the GUI features (like, menus and toolbars) - no-one I know who uses Emacs uses the mouse.
Another long time (15+ years) Emacs user here. I similarly use it completely keyboard driven. I have seen someone use it with the mouse, though. My PhD supervisor used completely stock Emacs to do LaTeX and actually used all the menus to do stuff. Quite eye opening for me.