Finland, Estonia, Latvia, Lithuania travel

I’m very interested in seeing these countries. I was wondering how many I might be able to reasonably fit into a week long trip.

I saw that there is a ferry from Helsinki and the other countries are connected by bus/ plane mostly. although I would prefer to travel by train.

also if you’ve been do you have any recommendations to do in the cities? which cities were nicest? also has anyone spent time outside the cities in cabins, beaches or camping? thanks