Army type/ theme

Hello all, My partner has expressed interest in soul blight graveyards as an army, and is quite an enthusiast in general when it comes to necromancy/ undead in other games.

The main question I really have is with the current eddition of the army, from what I can see a lot of individuals have stated specific models/ units are very hard tied into their respective sub-themes, so vampires with the new lord/ dragon model etc.

He likes the horde of undead theme with recursion. Are zombies and skeletons (Deadwalker/ deathrattle) seperate from one another with sub-faction/ rules/ synergy, or are there cross over with certain foot heros/ lords?

Any kinda pointers on what models to keep an eye out for with this type army composition with reasons would be appreciated.

Many thanks! =D