For us, the change wasn't really that big! It was obviously more work having to housetrain another dog. The toughest part was getting Brody onto a sleeping schedule and bathroom schedule.
I think you can feed the all stages food to a puppy
. You will have to slowly transfer him over though, which was a challenge. It was hard not getting Sophia to munch on Brody's exciting food. That only lasted a week until he was switched to her food. Not sure about the timing because I free feed both dogs. They share a food and water bowl. I used to have two of each, but they would only eat out of the same one anyway, so I moved a set into our office.
Brody was doing so well and actually peed on my blanket yesterday!!!! I, personally, think they're harder to train. Many people pad train their boys, it just wasn't feasible for us. Marking was only an issue in the beginning, he peed on the wall a few times lol, but that stopped pretty quickly.
Not sure what to do about Luma having free roam and the new dog. Maybe someone else can help you there.
Brody has slept on the bed with us since day 1 and it didn't cause any problems! Sophia has always claimed the feet area and Brody likes sleeping above our pillows lol. I think the biggest concern of him sleeping on the bed would be the peeing, not the dominance.
I'm not sure about what personality type is best, maybe just see what puppy she draws herself to when she meets all the little puppies!
I would guess a leader, if she is submissive. Sophia is the leader and Brody is submissive, and it works out perfectly.
SO excited for you and Tony!!!!!