One thing to be aware of: if you install too many addons, TM become finicky. Sounds will go nuts and the game will sometimes crash. The addons themselves just add weapons to the maps (since the weapon spawn points are random weapons, they will show up).
Also, always join a server with a default LDA tank. If you join with another tank, you can't connect and you leave a dummy idiot-IQ AI tank behind (idiot-IQ becuase it does about as much as a rock that keeps respawning can do).