I'll tell you about our car rental adventures in France.
We prebooked a Renault Megane diesel with a manual transmission. When we arrived the rental agency told us the only Megane available was gasoline and automatic. But when the automatic door locks didn't work properly they finally said, "Would you take a diesel?" Appears they had our prebooked car all along but (being from North America) would accept a gasoline automatic. About half the cars in France are diesels. Diesel fuel (in France anyway) is much cheaper than gasoline, and the mileage is much better. So get a diesel if at all possible. Lovely car by the way.
We didn't take the rental insurance but relied on our Visa Platinum insurance. We checked the car very carefully and noted all the minor dents and scrapes.
One day we were sitting in traffic in a small village waiting for a heavy truck to work around a tight corner ahead. When the traffic was just starting to move the car that had been sitting behind us for at least 5 minutes suddenly ran into the back of our rental car scraping our back bumper. Luckily the car was being driven by someone from England so it was easy to take down one another's details. What we didn't know was that we were supposed to jointly complete a tic box form in the glove compartment with all details that the 2 drivers agree upon. When we stopped at an outlet for our rental company later in the day, we were told we absolutely had to have that form filled out by both parties within 24 hours. Way to blow a day at the Riviera and drive half way across France! But when they found out we hadn't taken the collision damage waiver they said not to worry about it.
They insurance company at the 1-800 number was great. They said they expected to be charged the full cost of the repair but not to worry about it.
When we returned the car, we pointed out the scrape but the agent (noting that there was a scrape on the back bumper reported on the original condition record) said, "One scrape, two scrapes, what's the difference. Don't worry about it."
Our bill (which we received when we finally got home) was very similar to the estimate but included an unexpected "Surcharge Number 2" for 100 Euros. We wrote and asked what that was for and they responded, "Just a mistake, we'll take it off." We later learned that mystery surcharges are a common scam.
So a few adventures, but a lovely car for sure, and we sure learned a lot!