cruise would be almost totally on boat. Just get that vantage point of looking at these places from the water while having some good food and you slow float the best parts of the rivers....and you're sort of mentally mapping out your itinerary along the way for future days....like oh that looks awesome...definitely going to Strasbourg or whatever when we get off here... and you port up at night at a couple spots along the way and maybe sleep there....just so you don't miss anything due to visibility issues from the boat during the day. And you knock the whole thing out in a couple days and then you start driving, flying, or hopping trains for the meat of your trip depending where you are to get a more in-depth look at what you just saw off the boat.