I understand that some of the Tauck cruises also have non-Tauck travelers and I was wondering if that is the case with the September 2, 2019 cruise of Venice and the Dalmatian Coast.
Call Tauck and ask them. Have you had your Green book yet. As this is a Ponant ship, owned by a French company, any non Tauck guests are likely to be French. When ships have been mixed, negative comments have been made in the forum or on reviews.
When I took this trip there were non-Tauck travelers on the ship. My recollection was that there was about 2/3 Tauck and 1/3 non-Tauck. This had negligible impact for us.