I had trouble following your recent posting. It seems to be disjointed. As I stated earlier we have been on 12 ocean cruises in Europe and only three river cruises. To sum the difference -- Ocean cruises are far more flexible with many options from dinning times to excursions with a couple thousand guests. We tend to treated them as a floating hotel and travel vehicle. Almost all of our shore activity is self planned. We rarely to an ocean cruise's excursion.
River cruises are very different. Because of the size of the ship you don't have options for full size bars, all day dinning, entertainment, etc. Meal times on river cruises are fixed so it is a take it or leave it but we have never had any problem with that. BUT -- we seldom eat lunch on the ship either. We just skip it because we generally somewhere else. The food service is not available 12 hours a day as it is on a cruise ship nor is it as extensive. No room. It is amazing what the chef can do with very limited space. Second, it is very standard for most river cruises to include a half day excursion, generally a walking, guided tour of the port stop. Some tours have been so so but we have enjoyed all of them. General we stay in town after the tour, have lunch and work our way back to the ship later that afternoon. Most of the river cruises offer some optional, paid tours that may be all day or certainly for the afternoon. We have skipped some morning tours and nobody came looking for us or said anything about missing the tour. However -- we also advised the on-board staff that we would not be participating in the morning tour.
Because of the size of the ship and much smaller passenger group there is a tendency for the staff and other passengers to be much more friendly, attuned to your activities and schedule and know your name. You can not get lost in a crowd on a river cruises. River cruises are far more social than an ocean cruise. Probably should warn you that if you are a party of 2 you will be sharing tables with other guests. Since river cruises have more "inclusion" they tend to be more expensive than a similar length ocean cruises. From our experience we think they are worth.
From reading your other postings and comments, I wonder if you have developed expectations for the river cruises that will be hard to match. Still not sure exactly what you want. You claim to have hear negatives about Viking. What are the "negatives" you have heard about Viking or other river cruises?