Enjoy your cruise. The short cruises probably won’t give you the normal P & O experience as sometimes they might be used as booze cruises, also there will probably be a different clientele to the longer cruises . There probably won’t be a formal night on the cruise , I think it will tell you on your Cruise Personaliser before the cruise.
You can normally book some of the entertainment 2 weeks before the cruise. This is a new feature since Covid and hasn’t proved to be popular as most people like to decide on the day and I think they might be going to drop it on some of the ships.
Drinks etc are very good value compared to Cunard & Princess etc.
I think you can book some of the specialty restaurants before the cruise as well, I’m sure someone will correct me on that if I am wrong. We don’t normally book before as we normally have OBC and if you book before you can’t use it.