We took Avalon last year from Budapest to Prague. We arrived early because we wanted to spend more time in Budapest (Parliament tour, Hospital in the Rocks, Szenchi Baths, etc) The included tour had a running commentary by our guide and we passed by a number of landmarks. It had stops at Heroes Square and Fisherman's Bastion/St Matthias church. The tour ended in Buda, and those who wanted additional time there could stay rather than going back to hotel.
In Vienna, our tour included a ride around the Ringstrasse and then a walking tour in the city center. We could not go in to the Cathedral (Sunday Mass) and it did not include entrance to any attractions/museums. We went to the Hapsburg Palace and the Albertina museum on our own - also did a 1 hour tour of the riding school and saw the Lippizaners in their stables. Avalon offered an optional tour of Schoenbrunn Palace in the afternoon. If you are overnighting in Vienna they may offer a musical evening - concert in historic venue - we did it independently, went to the Kursalon
In Prague, our early morning tour went to the Castle district, St Vitus Cathedral, and then we disembarked from the bus in the Jewish quarter and walked with our guide to Old Town Square and the astronomical clock. The tour ended there. Avalon offered a number of optional tours, but we did chose to tour on our own.
Have a fabulous trip!