Disc A and Disc B are available for separate purchases, so it’ll be two different releases in two different release groups. But there is a set that includes Disc A and Disc B and also a bonus Disc C. Should Disc C be made into its own release in a separate release group with annotations that it’s only available in a set along with Disc A and Disc B, or should there be a release group that includes Disc C with Disc A and Disc B in a single release i.e. a three-medium release?
EDIT: I should add that all three discs each are still in their respective packaging.
That makes references pop-up when someone is looking at just Disc B.
I make use of as many of the relationships pointers as I can find. Link it all together. And splatter annotations all over the shop so people know what is going on. If I am reading up on Disc B then I want to know about how it was packaged and sold with the other disks.