You will find it easy to expand your borders and form a vast empire, just don't mess up early game. The Teutonic Order is too busy with Lithuania to protect its northern settlements well, and Lithuania is too busy trying to protect itself from the various factions attacking it to give much though to you. As long as you can protect yourself from attacks early game, you have the world at your finger-tips. The twin of the Russia faction in vanilla, and arguably the second worst enemy of the Teutonic Order, Novgorod is a faction with great possibilities. Once tensions start to rise, you'll most likely find yourself at war with most of them. The other factions can be allied with as long as you are against the Order. The Mongols can be allied with, but in my opinion, just taking them out is better, as that way you can better protect yourself from attacks from the rear. Novgorod should ally with you without any problem.
You need to plan your moves wisely and pick your friends and enemies well. On the camapign map, you are also in the dead center, and locked in a bitter war with the Order. In the mid-to-late game, you get some decent axemen and infantry units, and you also get some heavy cavalry to assist in taking down the Teutons. Hit and run's with your cavalry, along with the use of skirmishing archers and some militia to hold the line, should help you to win most battles early game. To get the most out of Lithuania's units, you need to focus on special tactics and strategies. As the description says in the menu, they have excellent light cavalry, which counters the heavy horses of the Teutons. Lithuania focuses on light infantry and cavalry. Oh, and did I mention that crusaders come from England and France to help you out? If you get one of those armies, get ready to do some steamrolling. Overall, the Order is a much-hated faction with superb, cool-looking units that can destory anyĮnemy unit, provided you can afford them. You don't have great light cavalry, but if you use your heavy cavalry well, you can completely destroy enemy formations. The Burgher Pikemen will help you hold cities while your Order spearmen, Prussian archers, and Ritterbruder destroy almost any early army they meet. They can withstand a lot of punishment and deal out a lot, too. The units you can field are superb, absolutely superb.
So much so that if you want to field more than one full stack army, you will soon be bankrupt. Adding to your disadvantage is the fact that your troops are expensive. Your position on the map - in the dead center - makes you a prime target and easy pickings for everyone. You will have a hard time defending your territory from the hordes of troops the Lithuanians pump out and from the ever-greedy armies of Novgorod. First of all, a good chunk of the factions hate your guts, and the ones that like you enough to form an alliance with you betray you later on. Playing as the Teutons, you will find yourself in a bit of a jam.
Those temples offer you great troops and bonuses, so they are definitely something you should use to fit your needs. Managing cities is the same as vanilla, however the Lithuanians have several unique buildings that should be used wisely. The most you will experience when playing as those other factions will be a port blockaded or a small fleet attacked. For the other factions, the sea is a small priority when compared to the other tasks at hand. But other than Denmark, only Norway will find the water important. Unless, of course, you decide to be a steamroller and just crush Poland and the HRE to get to the Teutons.
The only faction that will find the water important is Denmark, as the Danes need to cross the Baltic sea if they wish to invade Prussia. Water will not affect your campaign much. However, there are lots of patches of forest everywhere, offering the wise player the ability to lay ambushes. Aside from some mountains near Prague and in Norway, it's all flat. There are no choke-points or mountains or anything like that. It should be noted that the map is very flat. The map of the Baltic is well-done, and the music fits in perfectly with the theme of the campaign.