When I think of Paxi, I have in mind the tiny and gorgeous beaches around the island. I especially remember our trip to Antipaxoi island (there are frequent boats to Antipaxoi from Gaios), I think Voutoumi is of the best beaches in Ionian (along with Kathisma and Porto Katsiki beaches on Lefkada). Apart from the beaches, the rest of Paxi is a beautiful island, mostly Gaios, which is the capital. The port is lovely, especially in the evening, when small lights mark the streets and the boats. To see the rest of the island, I don't think there are buses but there are taxi boats from Gaios that go to other villages and beaches. Don't stay many days because there are not many things to see. I think 3 or 4 days are enough (unless you want to really relax), then spend the rest of your vacations in Corfu, which has a more cosmopolitan vibe.