I think you can tell by the shows if zigs are the one.
Proper head and shouldering, with those little fizzing trails as they head back down, I'd be chucking a pop up out, all day.
Slightly bigger shows/rolls, with slight flicks of the tail on re-entry, says to me to get on the zigs.
I agree you couldn't put a number on it. Imo it's completely relative to lake depth, substrate, conditions etc.....