If you are looking for a calmer and low-key place in Santorini, Petro's place is the best option for you. Peaceful location only 5 minutes to Kamari beach, where you can also find great food and restaurant options.
I would advise you to rent a car, as it is much easier to move to and from the house. Moving around the island is very easy, the furthest you'll drive is to Oia which takes about 30min to get to from the house.
House has 2 rooms and one bathroom, one twin bed, and one single bed. I would say 3 people fit more than fine. You have terraces from each room and living room where you can dry your wet clothes in the sun, or catch some fresh air. The kitchen is equipped to cook some easy meals like breakfast, or a quick lunch.
Petros is the most wonderful host. He is there for you in case you need anything. He also gave us an amazing tour of the island, he calls it the hidden gems of Santorini, and believe me.... they are! We would have loved to go on the first day just so that we had more days to go back to some of the beaches and places he showed us. Thank you Petros!