Auto-translated
Generally, the swamp castle is good. :) The melee fighters are good, and the flying units are fast. Hydras are deadly! Plus, the layout is convenient.
Still, it's not the swamp castle, but the barbarian castle that's the most inconvenient castle at the beginning of the game.
Archers aren't that important, but there's the possibility of neutralizing enemy level 3 monsters. Dragon serpents are awesome! This allows you to... like in soccer, quickly transition from defense to attack. Sometimes that's important!
Even though Hydras are weak in battles at their level, they are stronger than all the others when it comes to armies and tactics. :)