Paris to Interlaken via Dijon and Bern. About 11 days. About 100km (63 miles) per day. I'm flexible on the itinerary. My thoughts are first to Fountainebleau then across Burgundy to Dijon via Sens, Auxerre, and Vezelay. Then Bescanson, Le Chaux-de-Fonds, Bern and Interlaken. This is Part 1 of three parts. I expect to take the train from Andrematt to Locarno. I'll post Part 2, Locarno to Zagreb, separately.
I generally expect ot stay in hostels, AirBnB, and cheaper hotels. I like to eat in good, but not-too-expensive restaurants. I'm not a huge tourist, but all the towns mentioned above have at least a site or two worth looking at.