Hi Mifsud, and welcome to cruise-chat.com.
Is this the 12-night Baltic Capitals cruise (London, Copenhagen, Berlin, Tallinn, St. Petersburg, Helsinki, Stockholm)?
Although I've cruised Northern Europe a couple of times, I haven't been to these cities, other than London. You might try our Europe Port Chat
board, and do a search for your ports via the Find tab.
As for NCL tours vs. going it on your own, we've done both. Doing it on your own requires some research, which is -- of course -- why you're here.
Norwegian Jewel is a beautiful ship with many things to do. Have your cruised NCL and/or N. Jewel previously?