I consider Schinoussa to be a very calm island, at least off season. Chora (Panaghia) is a small village; it takes 2-3 minutes to walk the main street and sometimes you don’t meet a single person.
You have to be able to entertain yourself. But if you are visiting a island like Schinoussa I suppose you are looking for peace and quiet. Schinoussa is a perfect place for calm relaxation!
It’s an advantage if you like to walk; this is the only way to reach the different beaches, or to get anywhere on the islands. But relax, the island relatively flat.