I'd advice you not to take Estonia at all untill you're already wealthy. It's a very small province with low income that really only offers you a second border to Novgorod. As already mentioned it's also prone to rebelling. In my Swedish campaign the loyalty was down to about 120% (Very High taxes) in the late 14th century. By then I had owned the province for 150 years and had 300 men in it, one of which was the Duke of Estonia, a 7-star bloke with 4 dread. If a famine occured (which it does frequently) loyalty dropped to about 80%, and this was in Normal.