Which plan is best?

I always recommend being in your departure city the night before you leave to avoid any drama at the last minute, so I'd put Paris at the end if the trip. But I also would most strongly recommend against any long drives on your arrival day. Jet lag can lead to dangerous driving. But since a rental car for Normandy is so practical, I'd go with the usual compromise. Get into Paris and take the train to Caen. There are plenty of rental agencies near the train station. From there it's only a 30 min. drive to Bayeux. Finish your driving at a convenient town outside of Paris, drop the car, then train back to Paris.

don't drive after an all night trip, but also end the trip in Paris or you waste a full day getting back the day before on an already very short stay.

I would take the train to Caen on arrival and spend the night there -- get the car the next morning and finish in Paris. Or you might pick up the car in Caen and attempt the short drive from Caen to Bayeux that first day although any driving is not wise.

Bayeux is a short commute from Caen by train. Stay first night in Caen, go to Bayeux by train the next morning to take a full day guided tour, well worth the extra cost. Another night in Caen, where there are more hotels, restaurants etc. Next day hire a car Caen is interesting for half a day on its own, or drive back to Bayeux to see the tapestry and then south.

I'd probably train to Caen or Bayeux after landing, but that means guessing which train to pre-purchase (will the plane be late, will there be delays at Immigration?) or getting higher priced last minute tickets. Maybe spend the first three nights in Bayeux, pick up a rental car in Caen, drive to MSM and spend an night, drop the car in Caen and train back to Paris, spend the last three or four nights. Depending on your level of interest, something like
1. Arrive, train to Bayeux
2. D-day sites
3. Day-day sites
4. Bayeux tapestry, drive to MSM and spend the night
5. Drive Caen, drop car, train to Paris
6, 7, 8 tour Paris
9. fly home

What CJean said is exactly what we did and it worked so well. We did an Overlord tour for all of the DDay sites and that really maximized our time and took the stress out of planning that part of the trip. Highly recommend!

My husband and I did this very same thing but put Paris on the end of our stay. I know most people advise NOT renting a car and driving it out of CDG at 6:30 in the morning you arrive but we did.....I think the adrenaline kept us up and alert! We drove to Giverney the first night, then Bayeux, MSMichel, the Loire Valley and then back to Paris but we had 2 weeks instead of your one. Maybe after Normandy you need to go back to Paris as seeing the Loire Valley in all its glory would take too much time....save that for another trip. It is nice to be in Paris the day before you fly out so that these is no rushing about to get back there.

Personally, I'd spend days in Paris at the start of your trip. It's easier than going elsewhere and cuts down on an already big travel day from the U.S.

If MSM and D-day beaches are on your itinerary, I'd stick with Normandy or add a bit of Brittany. You won't have time to go everywhere.

In Normandy, you can add Etretat (and Fecamp), Honfleur and Caen. I took a train to Rouen, walked around for a few hours, then picked up my rental and drove to Etretat to start. You could even stop on the way at Giverny to see Monet's garden.

In Brittany, you could add St. Malo, Dinan and (a little stretch) Carnac (Stay in Vannes or Auray).

Either way end south and drop your car/train back to Paris from Rennes. If your flight isn't early, you can train in the morning. I usually stay one night in Paris before catching a flight out of CDG (just to be safe and avoid rushing).