Paris to Normandy - rent car at CDG or in Rouen or Caen? And a Mont St. Michel question.

I don't think renting and driving from CDG is at all like driving in Paris traffic (which I did once, bad decision ... ) But it would be challenging after a night of poor sleep on the plane. In any case, you need to read the rental agency HOURS carefully, which is easier to do when you rent directly from the company, rather than a consolidator site. Many places outside Paris are closed for lunch from 12-2, for example.

I don't subscribe to the theory that MSM is magical from dawn to 10AM. But if you want to do that, fine. I would not bother to sleep there, on or off the island, but many posters here report a magical experience in an overpriced, cramped room with difficult stairs, and limited, overpriced dining options. To me, one crowded stone street lined with faux medieval commerce stalls is pretty much like another faux medieval street. (Be sure to see both the street and the rampart walk.) We were coming from the Loire, and only spent a few hours, including in a crowd seeing the abbey itself. Now, some people of faith really want to attend a service. And please, pay your parking before trying to leave and blocking the exit while you fumble with the credit card payment!

Speaking of magic, is there maybe still an Alligator Farm along the strip of businesses leading through Pontorson?

https://community.ricksteves.com/travel-forum/france/travel-to-mount-st-michel

Take the train to Caen and rent the car there. More agencies, bigger selection.
It's only 30 kilometers, 18.6 miles, per professor google. Less driving time after an overseas flight.

In my experience, it is just as time-consuming to drive from CDG as it is to get from CDG to Gare Saint-Lazare and then train to Caen. But these days I almost always spend a day in Paris first to acclimate and see some sights on arrival. Last trip (2022) I rented in Paris by the periphery road and drove to Rouen with some stops en route, but typically I take the train to Caen. I believe that most people who dismiss the option of staying on MSM itself have never done it themselves. It is very different than a day trip—believe me. To dump your car and return to Paris, consider Rennes. There are rental offices at the train station there and a fast, TGV train to Paris.

Keep in mind that driving 3 hrs from Paris while jet lagged is going to be tough. We've done it and I had to stop a couple of times after catching myself microsleeping on the road. Guess some caffeine would have helped maybe.

Train is a good option if arriving early enough at CDG. Last time we were there we barely made the last train out to Caen. Make sure you plan it out.

Caen has better car availability than Bayeux. Drive to Bayeux is easy from there. Car rental within walking distance from train station.

Have done the MSM day trip from that area 3x. It's a solid day but plenty of time. I'm sure it would be very nice at night too, so probably up to your personal preference. Being there without crowds would be pleasant but takes some logistics to pull off. Up to you and how much you will get out of it.

Longues sur Mere battery, Ryes war cemetery, and Arromanches are also nice places to go in the evening around Bayeux.

With only 10 days your time is limited, but one option is to go to Rouen on the arrival day and pick up the car the following morning. This decouples flight & car, also gives you some rest (personally I like 3 days in Europe before driving, but that's me). The car rental in Rouen is conveniently located in the same train station you'll arrive at.

This plan isn't ideal because Caen is a lot closer to Bayeux, but Rouen has a nice pedestrian-only downtown and would be a good place to spend your arrival day (don't miss the light show on the Cathedral exterior). On the way to Bayeux you could visit Honfleur or Trouville (the latter if you like Impressionist art.) An alternative would be to go to Rouen, then the next morning take the train to Caen and get the car in Caen. Plan C, what I would do myself, would be arrive in Paris and spend a nite there, then take a train to Caen the following morning and get the car.

I would recommend a nite at MSM. We stayed across the bridge from MSM. You park your car right at your hotel, easy access to MSM on the frequent shuttles (or you could walk across the bridge), and it is beautiful lit up at night. Arriving at 4pm means daytrippers are leaving and it's a lot less crowded, but still plenty of day left for your visit. It was a high-point of our trip to Normandy.

I wouldn’t recommend driving straight from CDG.

When researching train vs rental car for our trip, it looks like it could take 6+ hours from the time you land at CDG to the time you arrive in Bayeaux when traveling by train. You have to get through immigration, possibly pick up bags, take the train into Paris, change train stations, wait for your train, then board the 3 hr train to Caen or Bayeux. The car rental place in Bayeux is in a gas station, and hours are very limited.

We ended up adjusting our itinerary so Bayeux was not our first destination, and driving ourselves when we were not jet lagged.