Roofing

Yes...........

It's my understanding the H clips are required when the rafters/trusses are on 24" centers but not if they are on 16" centers ....... but I'm a painter, not a roofer so I could be wrong.

Yes. I wouldn't span 24" with 7/16" OSB in the first place, but I guess it is done.

Yes, h-clips will be useful for your roof.

"Required" or not still use them!
Any OSB I've ever seen is stamped right on it the required spacing, which using H clips makes it easy to do.
Any mobile home roof I've ever walked on felt like you where going to fall through if you stepped between the rafters because they cheaped out and did not use H clips.
The worst one I ever did looked like waves from the ground.
Once I stripped the roof I saw something I'd never seen before, every piece had a huge stamp over the grade stamp that said in cap's "REJECT", it had been installed with 0 gaps so the sheets had buckled up between the rafters.