The cities of Europe are dramatic and beautiful but some of the best memories I have are when we were on small roads heading to places that weren't filled with tourists. You could spend all of your time in the cities on your itinerary and have a great experience and also have some time to rejuvenate or you could fill each day with dawn to dusk sightseeing, which is how we traveled when we were younger and enjoyed every minute of we traveled. Your initial comments suggest you'd like to experience more of the places you are going to visit than you could in the capital cities where people are pleasant but more reserved than you encounter in more rural locations.
How many of you are traveling? Are you comfortable driving? The Dutch and Belgian coasts have some great sights, so it may make more sense to drive, especially when you starting adding the cost of rail passes or tickets. I'd definitely recommend a night in Brugge, Belgium, and a canal tour while you are there; it's a good place to enjoy the ales of the region and enjoy moules et frite.
Whether you want to do day trips or stay in Normandy depends on what you want to see. If WWII history is drawing you into the area, there are the beaches and cemeteries as well as an interesting war museum near Caen. We have been to the region twice and still haven't seen Omaha Beach because we've used our time there to enjoy the coastal villages and If you want to see historic/medieval France, give yourself a day to see Rouen and Honfleur and another day to see Mont Saint Michel, booking a night near the abbey to see it at sunset and again at dawn; it is worth the investment of time. I will be heading back to Mont Saint Michel for the 3rd time this fall and believe it is one of those special places that is worth visiting whenever you are in the vicinity. On the other hand, three days wondering Paris and a day trip to Versailles is a reasonable plan as well.
Wishing you a great journey whatever you choose to do,