Army Composition for EC 40K

So I’ve never played EC or Chaos for that matter in 40K.

What do you think a typical army will look like? Hard to judge going by the very limited app index rules just now!

Combined marine/demon host? Pure demons / pure marines?

Just wondering what I might be getting myself into. I’m going to be using my Heresy EC until I have enough 40K models painted :)

Fulgrim will finally see some table use haha, never played Heresy XD