We will be in Paris,Chaminox,and Provence then back for a few more days in Paris .Should we rent a car when leaving Paris(no need for a car in the city) or take the train to another station rent and return the car from that station and take the train back to Paris? Would this way save a few more Euro/or Time? Lin
Arguably (I don't know your plans) you don't need a car in Chamonix either. So you could just rent a car in Provence.
You might consider grouping all your Paris time together and either (1) flying home from Marseilles or (2) taking one of the direct TGVs to Charles DeGaulle the day of your flight home. (Or fly into Marseilles and proceed Provence - Chamonix - Paris.)