Hey there! Seems like you got all the answers you needed, but since my experience was different, I thought I would throw it in.
On our China ABD we upgraded our room in Hong Kong, Shanghai and one other stop. We emailed the concierge in each city a few days before, asking for an upgrade. We were quoted a price and it was charged to our credit card on check out. The rooms on this trip were amazing without the upgrade, but we wanted a little extra space for the longer stays. It didn't change out ABD experience at all. When we got to the hotel our guide handed us our room keys and we proceeded just the way everyone else did. I did the same at the Lowes for our Backstage Magic trip. When I checked in for my pre-trip, I asked for an upgrade (which I would only want if I could keep it for the entire trip) they checked and were able to upgrade me for a fee which they charged to my credit card. The standard rooms at the Lowes were fine, but we had family coming to visit and staying in the hotel and we wanted a place for the group to hangout pre dinner etc. The important thing to note, though, is to make sure your leaders know your room numbers.