My local Wincos had a self checkout, and only have 1 or 2 cashiers open. They used to have two security guards and three cashiers managing the self checkout, with a massive line of people all the way to the back. It was like that for two years.
Today, I visited and they took the whole thing down, while having 5 checkout lines open. No security guards.
Real pleasant experience.
Yeah, I’ve found the best measurement is no more than one of the “small” shopping carts full. And not heaping full, mind you.