Haven't been on a Spirit class ship since 2018. Your pictures are making me remember how much I love them. Might have to make the ride to Alabama soon!
The change I'm referring to is that Platinum / Diamond rooms used to be completely ready when you boarded. (Way before 1:30). That is no longer the case. Just another perk that has vanished.
Since the change we have had both scenarios. Sometimes we receive an e-mail telling us our room will not be ready till 1:30 but we are welcome to drop off our bags and other times we have not received the e-mail. Either way we have dropped off our carry-ons with no issues. Just know that the doors to let you into your room's hallway will be closed with a sign on them telling you to come back at 1:30.
Just open the door and let yourself in.
At least 30 days prior to your sail date. If I recall we had to call the milestone desk ( in the link provided by BlerkOne) It wasn't something our PVP could do...but that was quite a while ago. I think we used ours on #28 or 29.
I find Excel class a little crowded / hectic for the first few hours after boarding and of course during debarkation. Other than that, I agree that everything is so spread out and there is so much to do it never seems crowded.