These are all conventions and you can change them, but I'm used to Meta = Opt and Super = Cmd on macOS.

That is incorrect. In vi and vim, "ESC" is the key that puts you into command mode (from insert mode). Command mode is the full-screen visual mode where you enter commands by a sequence of keypresses.

":" is the key which issues "ex" commands. vi and ex are two different modes of the same editor. Any command which begins with a colon is an ex command, not a vi command, not done in "Command Mode".

True. ":" is the rough equivalent to M-x, though.

Also worth mentioning is Q , which puts you in ex mode, essentially just ":" prompts one after the other until you exit or issue a "vi" command to go (back) to visual mode.

And then there's open mode, but vim doesn't implement that.