After going on 10 ocean cruises with Princess, we've booked a river cruise on a Viking ship. We've heard shore excursions are included in the price but you can book others also. Who can tell us more! And any other differences between large ocean cruises vs smaller river ones, besides less people on board.
In Vienna I rated the optional Mozart & Strauss Concert; see this recent thread (on River Cruise Ports) about it, there are opposing views - Vienna concert? - River Cruise Ports - Cruise Critic Community
We saw the Hungarian Horseman (see below) - I see on your tour its optional from Budapest - and I cannot remember if it was included or optional when we went from Budapest to Bucharest in 2019 but the show is amazing, and was a really good trip worth paying for.