Yeah, if you have your own car brought with the ferry or you rented one (expensive compared to most countries) then 4 days would work. If you couch surf and the person is cool enough to take you places then would work too. Still, if you used the buses the distances are not great and allowing for the bus/ferry schedules you could the places you mentioned at a leisurely pace in about a week.

I´d say it is not. Only if you are traveling with your own car.