He would still have 3-4 times more troops) although with 3 castles, the unit growth for the player is higher.

Yeah)) + you could create a second hero with a dwarven army. The only thing is to get the mentor's education. After the dwarven army, the demons would still win anyway))

And the fact that the growth is higher - what's the point of it, subjugation on the thanes, and the rest will just be standing at the gates. If he even makes a hole - blind the one who crawls into the passage. And if he also gets a berserker - it will already be a beating, in my opinion.