Pochita spoke to Denji in his dream right before he gets out of the trash container.
To me this indicates a direct mind to mind connexion as Pochita was fusing with Denji.

Cop said Denji isn't possessed because Pochita didn't take control, it transfered all of his powers/abilities to Denji and supposedly abandoned his own spirit/life. But maybe not. After all Pochita said it wanted to see Denji's dreams fullfiled, as in be there to watch them happen.
I don't know if it really makes a difference. We'll see if the subject is ever coming back.

I like the fact that not all demons are necessary there for evil deeds. Pochita probably had his needs involving sucking blood and maybe we'll get flash-backs to clarify this. But in the end it did something so selfless. So for now we have very basic demons to be treated as mindless beasts (tomato and others), evil ones (zombifier) and Pochita class. I guess the later is the rarity for the show to provide enough gore action scenes.