Something happened in this tuning session that has never happened to me before... The default tune out of the box was VERY GOOD. In fact, I was almost entirely unable to improve upon it!
That doesn't mean that there wasn't room for improvement. But every little thing that I did to try to make things better just made things worse. So I would say that this copter comes from the factory with the best possible tune already on it, but it's possible that it could be better. How? I don't know... different motors and ESCs most likely. Not that these are bad, just that I'm not sure what else there could be. Maybe tweaking the Betaflight filters, which is a step I haven't gotten to yet.