Your Division is simply your GP bracket at the start of each Championship. Divisions are set the rules and rewards that you are chasing each Championship. Your Division will be reevaluated at the start of each Championship and you’ll receive greater overall rewards the higher the Division you qualify for. You can’t change your Division until the next Championship, but you can reach higher leagues (Bronzium, Chromium, Kyber, etc) within that Division during a Championship to receive better rewards. As your GP creeps up across the five-week championship, your Division will still not change. Leagues are fundamentally the milestones for you to focus on as a player within a Championship. Also note - your inventory is not locked during the Championship (inventory locking per Grand Arena round still follows the same rules), but your Division is.
I wish it were a little more clear, but it does say you are locked in for a round of GA, so I would think that means "the week" i.e. - the 3 match round we are in right now.
It should be locked. You shouldn't be able to take off all your mods to get an easier matchup and then put them all back on. It means your gp wouldn't have been fairly matched if you could do that.
Replies
https://forums.galaxy-of-heroes.starwars.ea.com/discussion/206074/grand-arena-championships-gp-divisions
I wish it were a little more clear, but it does say you are locked in for a round of GA, so I would think that means "the week" i.e. - the 3 match round we are in right now.