When live coding on a Mac, don’t just mirror your screen as no one will be able to see what you’re doing. Use, e.g., SwitchResX to mirror your screen at a larger retina resolution (1280×720 works if presenting on a 1920×1080 projector).
That way, you shouldn’t have to alter the text size in your terminal, browser, etc., and the audience will still be able to read your screen. Also goes for live streams, etc.