Yes, the undead do seem a bit powerful. I was originally going to make them even more powerful, by having them turn defeated enemies into new armies of the dead, but realised that was so overpowered it was just nuts.
I'll turn down their power in the next version.
Regarding the number of agents, that's already a parameter in the parameters file, so it should be a very easy change. I'll add something to the game options screen to allow players to choose it when starting a game.
There will probably only ever be one noble enthralled, because the UI becomes painful to use if there are multiple. So many voting screens popping up at all times.