Setting the levels equally to start would help, but doesn't control when someone suddenly gets loud. With compression, you can increase quiet sounds, decrease loud sounds, or both.
A type of compressor used to limit the maximum signal is a limiter. "Limiters are common as a safety device in live sound and broadcast applications to prevent sudden volume peaks from occurring."
Probably a lot of the problem GP is describing comes from people having inconsistent distance to their microphone, moving around a lot. Then using an audio compressor effect plugin is an appropriate answer.
I've often thought about adding a compressor pedal to my TV sound system. It would be excellent for when you're watching action movies with hard to hear dialogue mixed with loud noises, and the kids are asleep, so you spend the evening turning volume up and down eight times per minute.
https://en.wikipedia.org/wiki/Dynamic_range_compression
A type of compressor used to limit the maximum signal is a limiter. "Limiters are common as a safety device in live sound and broadcast applications to prevent sudden volume peaks from occurring."
https://en.wikipedia.org/wiki/Limiter