So in my experience, I don't care if the irons hit each other, but I use the Stiff arm in a soft case. I wrap the stiff arm because the brass endings on that leave big ass scrape marks on the iron heads, that annoys me when the top of the face has a huge scratch.
So I wrap the stiff arm in my towel to make sure it doesn't scratch the faces, I don't mind banging chatter though.