Grip number is entirely dependant on the handle in my opinion, and also the situation the bat is used in.
Most of my bats have one grip. My Laver has a handle like spaghetti though, so it has 2 grips.
I have a Vitas Cricket Lion Roar which i use exclusively for T20 bunting and sixes tournaments, ie see ball hit ball, no time for feel or finesse. This has a thick handle anyway, but i have two very thick grips on it, picks up much lighter as a result. And as i am only batting for a relatively short time, it doesn't matter too much that i can't really hold it to play proper shots, just swing from the hip.