I just did this last weekend. It is a lot of work. I doubt many do this because of this. I boxed it in completely with 2X3 or similar as appropriate to get the correct dimension width-wise for the light. You could simply box the ends and not the sides but that is not optimal because of the method of cut out.
I use a rotozip to cut out the ceiling for cans and these troffers and I need something for the rotozip to guide on. The framing satisfies this need. Without the framing you are not going to do as good a job on the cut-out step.
As for the rough electical, I test fit the fixture and made sure my romex was long enough and in the right spot. I stapled it within 12 inches of the fixture's box. I preinstalled an NM cable clamp and snugged the screws. I pre-scored the jacket with the Klein stripper so that I can reach up as installing the light and guide the romex down and through the hole in the fixture box. Then I can secure the fixture, and then apply the locknut to the nm clamp, pull the jacket on the prescoring and finish the wiring.
Troffers like this are the best possible look but major expense, both in terms of fixture cost and installation. That's why you never see them.
There was a guy on here that did this before and he put up some nice pictures of the frame out.
You do not hang the light for rough in inspections. You box it up with framing, sheetrock, cutout the sheetrock and then install the light.
