Hello - I would especially appreciate an answer from Epic staff, if someone is available 
However, I have a need to know if I have set up level streaming correctly, and I will describe exactly what I have done so that you can tell me whether or not I am on the right track, or off
I am part of a small team working on an open-world game. The map is approximately 250 sq km. I have been following the ‘World Composition’ tutorial, found here in the site. The world is divided into 12 equally-sized sections. Each section has a level streaming volume bp (again, from tut here on the site), a post-process volume, and a lightmass importance volume. Is it necessary to have lightmass and post-process volumes for each section, or is it better to have just one of each covering the entire map?
As I have played the level a few times to check what I have done, it seems that moving from section to section works as the blueprint says that it should, though I have not a clue as to how one can tell if it is working as it is supposed to (this is my first attempt at level design).
Any and all help is appreciated, particularly if you think that I may have missed a step somewhere along the way