We will fly in and want to know if a car is preferable for 2 nite stay?
This is a hard one to answer. We went to Santorini for 4 nights in 2018, flying in from Athens. We rented a SmartCar, easy pickup and dropoff and a fair rate.
We used the car to go to the Akrotiri ruins, the old lighthouse, and between the airport and our resort in Oia.
BUT ... driving on Santorini was the worst travel experience of my life. Narrow, windy roads with crazy drivers coming the other way. The crazy drivers range from drunk teenagers on 4-wheelers to giant tourist buses. Driving anywhere through Fira will get you lost in a maze of one-way streets, dead ends, blocked streets and (more) drunk teenagers.
On the other hand, getting around Santorini by any mode other than car is not super convenient. Buses are irregular and crowded. If you absolutely have to get to a point far from your hotel, I would take a cab.
If I were to do it again, I would not drive. I would get a cab to a resort in Oia, and spend all my time around the pool or walking through Oia or swimming in the caldera below Oia.