Best transportation method Paris to Bayeux

There are direct high speed trains from Paris to Bayeux, several per day, or you can also transfer in Caen (but why bother?) It's only 2 hours so this is MUCH faster (and easier) than driving. Bayeux is pretty walkable.

For tourist sights, the Cathedral in Bayeux and seeing the tapestry are the two big highlights, but you can pretty much see those and the town in a day.

I suggest a train to Caen, where Avis and National have offices right across the street from the station. It's a short drive to Bayeux from there. The rental office in Bayeux is some distance from the station. But check whether you can drop off the car in Caen on Sunday, some offices are closed that day. If your Monday flight is from CDG, you might consider driving back there Sunday from Bayeux. We did that and had time for a side trip to Honfleur. No problem with returning a car Sunday at CDG. There are numerous airport hotels that make it easy to catch a morning flight. Auto Europe is a good way to shop for car rentals and make a reservation if you decide to go this way.

Alternatively, since you'll be on a guided tour Saturday, you might forego driving and just take the train to Bayeux, see the cathedral and tapestry on Friday, take the tour Saturday, and do something else in Bayeux Sunday before training back to Paris. But getting out to the airport the night before a morning flight is still a good idea.

Both Bayeux and Caen have World War II museums. Different in approach but both worthwhile. Bayeux's is out of the center of town but walkable for folks who don't mind the exercise. Caen's much larger museum requires a bus ride from town. Or a taxi, of course.