I know what you are on about, and yes, I know old musicians who receive royalty payments from PRS and they are all sound people.
Years ago, I played in bands and there was usually one such person as you describe.
Overbearing egotistical maniacs with limited ability that had raised voices.
It goes with the territory.
I was just happy to play along and have some fun, but they always had to have the last word.
I gave up playing in bands years ago as I wasn't really that bothered about becoming a star, but I've got my keyboards and stuff at home and I enjoy playing as much as I ever did. Enjoyment for me is the key, and I can play whatever I want without the inquisition.
Playing music is the most calming thing I do. I've never tried Yoga or whatever because I don't think I have to.
Spending a few hours tickling the ivories empties my mind, and that's all that matters to me these days.
It's a great way to relax.