A Blackwing Volume release is just a regular Blackwing pencil with a different design. There are most of the time not any other differences. There was a time when one of the core’s wasn’t available outside it. But these days all the cores are available as a regular edition.
What makes a good one? I think the design has to mix the theme of the release, it has to look great and either be unique or a really good looking version of something existing.
When I say look great, that doesn’t mean I like it. Just that it is a well designed version of what ever it is.
Some of the Blackwing Volumes have been very unique designs like the comic book one. While others have been their own take on something that someone else are already making. For example like the Staedler Noris. I don’t think it is a problem as long as Blackwing makes it look amazing. The $25 or whatever a box of Blackwing costs today of some random pencil should be the perfection on it. And I think Blackwing did that with the Noris like edition they did a while back.