Wondering whether that mix knob on the M4 would be of use to me (as I don’t stream or podcast). If not, then M2 may suffice, as there are no other differences. I guess that mix knob will be present in software too,
Meanwhile, more info from the future on what’s coming:
iZotope launches Dialogue Match with reverb adjustment: https://webcache.googleusercontent.com/search?q=cache:1cjrQX3rufQJ:https://www.izotope.com/en/learn/the-technology-behind-the-reverb-module.html