Regarding the first point – 3 levels are sufficient, maybe even 2 (it depends a lot on the army), and more specifically, the total HP of the units.
Regarding the second – no more than 4 buildings per day, in my opinion.
3. When the city is destroyed, it will be unavailable for seven days, and then ghosts will settle there, and you can take the city back.
4. You can build two types of cities, but for the builder, not for the destroyer. If you destroy a Rampart with Solmyr, and then come back with Sylvia a week later, you can build a Castle and a Rampart.
P.S. In my opinion, seven days is very long, so I practically didn't use it.
But even a hero of level 6 with almost no army will not be able to destroy buildings.
2. Moreover, each subsequent destruction of a building
(in one day) increases in price. When destroying an upgraded building, it is destroyed completely, meaning it will take 2 days to rebuild.
