Tactics for the Swamp (Fortress).

Castle and Rampart. Upgraded archers and moved on. Very simple cities to play with.
Dungeon is, in my opinion, stronger, but you need to know how to fight with troglodytes there, without losing them senselessly.
And with the Swamp, 12 gnolls will come at the start, and you'll win. That's why newbies don't like it. (Although, Thazar wins easily).

But when upgrading archers, you can end up with cavalry against the Castle, which, in my opinion, is critical. On the other hand, the attack power increases. Here, of course, you need to see what is happening around and try to get an understanding on the first day of what neutral creatures surround the castle and what bonus goodies, like crypts, are nearby.
And about the elves, you know:), it's not always the case that you get at least 6 basic basilisk shooters at the start, and there's no point in upgrading if you have less. Although, to be honest, upgrading 50 centaurs might be even better.
In any case, I agree that the attack power of the Rampart at the start is indeed considered one of the most serious.
Oh yes, I forgot to mention. :) I only play at 200%. :)