Removing the interior panels, or making sure they are securely fastened, is easy. I can imagine if there was some play in the panel that one or more of the clips could squeak. It is metal-on-metal. Best thing I can tell you is to pull the panels one by one to isolate the noise, and then apply a small dab of grease to the clips.
If you want to be sure of what you are doing, fold down the rear seats and have a helper apply pressure to the panels when you are driving. It should be obvious at that point, and should tell you to look elsewhere for the noise, if that is the case. If the panels are rubbing together where they join, I'm not sure if applying a little Armor All to the panel overlap will help.
I've removed all of the lower rear panels a couple times for one reason or another. The clips won't break unless you twist them or pry up/down on them. I haven't broken one yet. Just start with a corner and pull straight out. After the first one, the rest seem to pull out really easy. I was surprised by how much dog hair I had under the panels.