We did B2B on the Dream a couple of years ago for DH birthday. We are platinum and were able to book a cabana on the first (3 night) part but not on the 2nd (4 night). I think more newbies on the 3 night cruise. We were also able to book the same rooms (connecting rooms) so no need to pack up and have room stewards move the luggage. That was a good advantage.
I don't know about photo package. We got all of the tastings we wanted but assume that was because we are able to book early due to platinum. If you are gold before the first of the back to back, your booking window opens earlier. If you will be gold on the 2nd part, it does not apply because you have to be gold before you can book earlier. Does that make sense?
Last day - first day - I did laundry the morning of the last day of the first part of the trip. Laundry was wide open, no one else doing it. I was up early so I washed and dried before we disembarked. Our travel relatives, washed before disembarking and dried when we got back on.
Process - make sure your room steward and your dining team know you are back to back - you can request same dining team and they will make it happen. Make sure the room steward gets you the 'paperwork' you'll need to disembark. (ours did not)
You should not get off too early. We waited in the atrium until most of the people were off and the line to get off is shorter.. (travel mates put her clothes in the dryer, just before we got off.) You have to go through customs, as you would any other cruise, so make sure you have your passports and ids, etc. And something to keep you occupied during your time off the ship.
After you go through customs, you go back up the elevator and check in again and go to the 'concierge' waiting area. We were off the ship for about 1 hr. Travel mates were able to check the kids into the kids club again while waiting. Getting back on the ship is simple but no pictures and no introductions when entering the ship (I did my own
) We went to Guest Services to get on a wait list for a Cabana (did not happen) and then we could go back to our room. Travel mate finished her laundry. We went to Cove cafe (it was open) got a refreshment and then the kids went on the Aqua duck numerous times. It was very relaxing, this 2nd embarkation. Not as rushed as embarkation usually is. We liked it. We enjoyed Castaway Cay twice, almost did not dock on the 2nd time but we made it. We do not do Nassau, and treat it like a sea day.
I would do it again. Only negative I would say if they are not strict on keeping under age people out of the adult areas on the 3 day cruise.