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1) Regarding the two-story dungeon: Well, it's the same as in your new map – it's best to leave the dungeon as quickly as possible, as the enemy's armies accumulate quickly at the beginning.
2) Regarding the transformation of dwellings – I know about that... Although, in theory, they are completely typical...
3) Regarding strengthening the neutrals – it's possible. It just so happens that archers cause more problems.
4) And where did I miss such a "good" squad of succubi and ghosts? I can assume that these are ordinary neutrals, but in that case, there shouldn't be many of them.
5) The side is chosen when you approach the Elven castle or the Necromancer at the cemetery. More precisely, there will be a dialogue and a quest box. The choice of side affects the further development of events on the map. And for now, since you haven't chosen a side, you can freely kill everything =)
6) The Elves have only a city.
Thank you for the compliment about the graphics; it did require a lot of work. There was also a beautiful Dungeon, but it was removed. It's not as good after restoration.
upd: I wrote this post a long time ago and forgot to send it. You have already found the answer to some of the questions. =)
Added 3 minutes ago
It turned out to be fun with the peasant, yes. The thing is that you can simply take the boots from his enemy and run away, or you can trade =)
The Ents are a separate matter. If you form an alliance with the Necromancers, then when you enter the shipyard territory, all the Ents will flee, and the shipyard will be destroyed.