Another thing to consider is whether there needs to be a commander-based bracket list where decks running certain commanders can never be lower than a 3.

The boundary between 2 and 3 specifically needs more definition. What is the minimum number of turns a deck can win? What does it mean to be optimized? It's not an easy line to draw but someone has to do it. I do feel strongly that the bracket system has made commander more enjoyable overall!

Neither, you should use the grieves on a commander that you need to turn sideways to do a thing.