If you arrive early they probably won’t let you in, and it would definitely be too early to board (by half an hour or so) because they will still be cleaning the ship from previous cruise. But don’t fret…..go at your assigned time, join the queue and check-in should be easy. You will be among the first to board the ship.
if you have been used to looking for dedicated check in lines for Concierge, Elite, Aqua, etc. you won’t find them. It’s all done by assigned time now.