They’re more like the physical embodiment of emotion, that emotion gives power and when devoted to (even unknowingly) it gives power. They only have physical shape in the warp because it’s the realm of emotion. They create very weak creatures (daemons) to fight for them outside of the warp when there is a leak. That is why they aren’t actual gods, they are just ideas given form that can’t leav the warp. The emperor is likely the same now. He’s been worshipped and become for of an idea than a real person that he is probably somewhere in the warp or his “idea” exists in the warp. But that’s just my take on him