How does chainsaw thing compare to Hellsing?
That series has no real stakes (well, for the protagonist) or character development (well, mostly) and it's a stone-cold masterpiece. 
I guess in your description it'd be similar.
Chainsaw Man is basically: "Denji is homeless and has a pet chainsaw dog (as seen in Toku's post) that gets attacked by "devils" [like his chainsaw dog] and dies. His dog is sad about it and becomes his 'heart.' Mikami [or however it's spelled] the head of a devil assassination/killing firm in Japan finds him and hires him to be part of the group. He has a huge hard-on for her and agrees [along with the fact he will no longer be homeless]. That's it. That's the plot."
But it has no plottttttttttttt.
Judging by the author's prior work (Fire Punch), it's better off without one.
I haven't read that one. But man, Chainsaw Man is just stumbling from one plot to another. The bomb devil that works for the gun devil that was planning to kill/steal(?) Denji to Russia was the most interesting part beyond Mikami killing criminals to smush (literally) remote criminals that tried to kill the entire Tokyo branch of Devil Exterminators [along with her] via her devil summoning thing.
...Then they went no where. Mikami is still a mystery (for frustrating), Bomb Devil fucks off back to Russia (only to return in the future) and since then it's been "ME SO HORNY!!!!" or "MUST KILL A BUNCH OF DEVILS!!!!!"
Seriously, this is the most interesting part of the series, and they do jack-shit with it right after (beyond making Denji marked for death, I guess):

(lol at linking a pirate one because I can't link the actual chapter without a $2 paywall. I understand why, Viz, but sheesh)