No need to reserve more than 24 hrs in advance. I am by nature a planner and quickly learned to let go. The 3 places suggested above are the ones I'd pick. They are not places you would spend a day in if you were touring France by car, but if rest is called for, they are the places with the most distractions.
I took a rest day in Cahors because the weather was much hotter than I like. Not hard to fill the day exploring the old quarter, the market, and the cathedral; write postcards; search out the hidden gardens. I would have stayed wherever I was that day because of the weather, and not reserving allows you to do that.
Another time I took a short day because of heavy rain and walked just from Condom to Montreal sur Gers. Montreal is not a place I'd ever suggest spending a lot of time in, but lunch under the arcade on the town square was just what we drenched souls needed, so it became a half day of hiking and a day to "chill".
A day off in Figeac allows you to visit Rocamadour by train. An easy round trip. Highly recommended.
Moissac? I once visited by train (30 years ago before I learned to walk) and missed the train I planned to take back to Toulouse. Waiting for the next train, I was forced to stroll along the canal and read, watch local kids come home from school, search out an ice cream. The nicer parts of Moissac are not those you trudge through on the chemin.