We were just down the hall from the OP and share many of his observations. Everything on the ship was open, but with only 353 pax many features were under utilized, at least by us. We didn't need the retreat lounge (except to grab a couple of Evians) because the bars were not crowded. Always a seat at Martini Bar. We didn't use the Retreat sundeck much because it offers no wind buffer, and the wind was 20+ nmh for much of the voyage. There's also no rain cover or shade so the weather needs to be perfect for the Retreat deck to be of value. Friends now on board (with 5 times the passengers) report a very different feel. We were spoiled.
As Bob mentioned, we know of only one COVID case, as it was in our hallway. The passenger was not moved from the room...I believe because wheelchair access was needed. Whether you book next year is really not a decision you should made based on this very unique capacity experience. But based on the suite layout and balcony situation, we would opt for AQ aft on deck 11.