I'm confused about nanodiscs and my reading thusfar has not been very helpful.

Are there different nanodiscs that should be used for inner membrane proteins vs outer membrane bacterial proteins? My understanding is that the two membranes are of differing composition, so it would make sense. On the other hand, nanodiscs themselves seem to have their own composition. Are there differing protocols at least?

In general, nanodiscs seem to be extremely helpful for structural studies. However, the disc clearly obscures the membrane-spanning portions of the proteins in question. The transmembrane helices must not be that interesting for structural work then? Or is this a major drawback?