We will be renting a car in St. Malo, then drop off somewhere near Paris- We will be at a home base in Normandy for a few days before driving to Paris- it occurs to me on the map that Giverny(2 hours from our BB) is on the way to Paris- would it be reasonable to see Giverny in the morning and then drive to Versailles(55 min from Giverny) to drop off the car(would like to avoid driving into Paris) and see sights, then take the train to Paris in the evening? Or would that be too much for one day? It would likely be on a Friday, then Paris- Sat, Sun, Mon(Versailles is closed Mon and supposedly super crowded Sat/Sun) before we fly home Tuesday. We will be there the first week of April.
This doesn't answer your full question, but in case it's of interest--I've had a reasonably easy time dropping off a rental car at CDG when approach from the north, northwest or northeast. Then catching a plane, or taking transport from CDG to Paris center if spending time in Paris.
It goes without saying, if you're staying in the Paris center for a portion of your trip, you don't want a rental car.
Its theoretically possible to see both Giverny and Versailles in one day, if you get a REALLY early start. Bear in mind you have a 2 hr drive to Giverny plus an hour to Versailles, plus time to drop off the car before the agency closes. That doesn't give you very much time at either site. Versailles closes around 5:30 I think. Personally, I'd pick one or the other to avoid being rushed.
Thanks! That helps.