Hi Claribo! Wow, a 27 day trip is too long for me. As I mentioned, we love to eat but after 6 consecutive days of eating restaurant meals, we started to cook some simpler meals at home. I don't think I could handle a 27 day trip! We were in France for almost 12 days (that includes a travel day) and that felt plenty long to me. It's also a matter of kids' school and budget for my family. If you're able to travel longer, I think a leisurely approach is best so you don't feel too overwhelmed/exhausted.
I know renting a car means you can stop at more small towns. However, I find it stressful to drive in foreign countries where we don't speak the language, can't read the signs, etc. So we have never rented a car. Of course, we have only traveled to a handful of foreign countries and found grabbing a taxi more convenient. These days, many use apps so we don't have to speak the local language at all. I just enter our destination in the app and greet the driver with a basic Bonjour or Bonsoir! There are also plenty of taxi drivers who speak English in a wide variety of countries, so we've been fortunate in that way.
Have a great time planning your trip to France!