No worries on mentioning competitors… it’s not like they are secret and hidden from Google search. In fact, theme sites are pretty much in a friendly competitive realm. Everyone has advantages and disadvantages and it gives the end-user more options to choose a theme of what works best for their needs.
Regarding the “100% sections” you mentioned, this is actually done from a plugin level and generally is associated with page builder plugins. I am in the works with a developer of a very popular one which has this capability, including doing solid background colours, image backgrounds, and even video backgrounds.
The other type of 100% section is associated with Parallax websites where you scroll a page and sections with images in the background scrolls behind.
Which method were you referring to, the static sections or the parallax scrolling type?