Note: Next version here.
If we visit a single country at a time, it becomes easier to optimize for and understand the public transportation situation. A 10 day trip plus ~2 days of travel sounds like a good idea. Train tickets: The official website to book train tickets is SNCF Connect in France and SBB in Switzerland. Another one, likely a travel agency, is Rail Europe. In at least one case, we found cheaper tickets here compared to SNCF. EU Rail passes can also be a good option. Tickets can be pretty expensive closer to travel time. Book at least 1-2 days earlier. Book hotels and apply for visas, both as early as possible. Helps getting good prices. It’s often cheaper to book directly with a hotel compared to going through websites like booking.com. This time, I didn’t plan much before arriving here and that wasn’t a great idea. I should’ve briefly checked online what activities are available in every city we visit, so that we could book the more popular once earlier. Search for 1, 3 etc. day (travel) passes. Can be cheaper sometimes. Also, check for country specific train or travel passes. Can be cheaper. Pack light: it helps a lot. Don’t cheap out on cellular data as it gets used up quickly. Google Maps eats a lot, so download offline maps through wifi. (For e.g., 6 GB is barely sufficient for a 20 day trip, assuming there is wifi in hotels.)