Put in the hatch so that there is future access in case anything up there needs to be serviced, technically the bottom cord of trusses aren’t designed to hang heavy stuff from nor to use as a storage platform but everyone does it anyway. Drywall is a fire barrier vs OSB which would be highly combustible, I don’t think OSB would pass building inspection inside of a garage, especially on an adjoining wall. Wire for some speakers for a stereo.