My two cents: pochita is khaos
Pochita is the chaos/void devil which is the og Greek god that birthed the other major gods that eventually birthed the Olympic gods.
In Greek mythology chaos is more the void or empty space rather than disorder but fujimoto I think uses the double meaning throughout the manga.
I think pochita is also a stand in for fujimoto themselves as well. The god of the chainsawman verse in meta terms is the writer no?
Few points, there's many layers here and it's going to sound chaotic as you read it as it's bits and pieces or hits all over the place:
It's pretty romantic for the control devil to want to control the chaos devil more than anything. Makes sense right it's what I'd imagine the ultimate goal of control is, to control chaos.
I think the umbilical cord that is always going off screen is symbolism for pochita being meta to the story. It comes in from outside the universe/the panels of the manga to spice things up, pochita is always the highlight big moment in the story a nice surprise when the story starts to become a bit contrived, chaos appears! Why it's meta is that I think it's a conscious choice of the writer to change the flow of the story by subverting expectation this is what pochita represents. Chaos.
When pochita eats a devil that's that devil returning to the void as they become a part of pochita/the void. The void can puke/birth them back up at will even. No concepts existed before khaos/void brought them into being and so at pochitas whim these concepts disappear back into the void when eaten.
(Ending spoilers)
Pochita just deciding to become this kids heart just to see what happens. Pretty chaotic neutral thing to do if you ask me, then just run it back as if it never happened. Also pretty chaos coded. Pretty powerful being coming down to the world of humans desguised to just be a part of the story for a while then leaving as many of the Greek gods in myths did coded.
The ending is just pochita returning to the void, it would be no big thing for the original god to just restart the universe/story and decide not to participate this time around.
Anyway I think fujimoto just got all meta with the ending of part 2. He probably personally wanted to move on from this story and so if fujimoto is leaving the story then pochita is leaving the story. Now we all must live in a world without chainsaw man within the manga and outside in the real world.
Get it? There's no more chainsaw man.
I could go on and on about the metaphors but hopefully this prompts some fans to think on it themselves.
That's my Theory ;)