How difficult is it to get on trains at specific times with the flexi pass? Our travel days will be long and we are going from places like Normandy to Chamonix Monte Blanc and are concerned about getting to Chamonix at a decent hour.
Getting on trains requires you to be at the platform at the right time. So that is not going to be the issue. The real issue is that some trains require seat reservations. Those seat reservations are not easy to get in countries that have included reservation ticketing. So for example in France you are better off just buying tickets directly form the operator, and not bothering with a pass. A pass is for people who do not plan train travel in advance.