This series feels like it takes place in the exact same universe as Tiger & Bunny. Both are set around a world where super heroes are celebrities & their careers are a popularity contest. The biggest differences, aside from Tiger & Bunny not being a comedy, is that T&B focuses heavily on sponsorship & television, while Onepunch Man spends a great deal of time mocking the hubris of the heroes & monsters, & the entitlement & blind optimism of the citizens in a world where the only character with two brain cells to rub together is a 10 year old child.
I'm nearly convinced that One speed-draws this way intentionally to give it the look of a child-drawn comic for comedic value, but sometimes he uses enough detail that exposes that he's far more capable at art than he lets on, & his art improves over time, just nowhere near Yuusuke Murata's level.
This webcomic collection serves as a storyboard for Murata to work off of in the manga, as well as provide fans with years of spoilers of things to come.
It's not exactly scene-for-scene, as One may change, add, & drop things from this book for the remake.
With the sorry state Marvel & DC have been in for the past 5 years, I think it's safe to say that Japan is the future of super hero comics.