Hi @james-woods_8996 ,
You are correct - in a mirror scenario, either side could publish (or delete) packages, and it would be propagated to the other. Three-way is also possible, but you do that with two two-way relationships, if that makes sense?
So it's basically A <--> B + B <--> C, and that means if you publish/delete a version on A it will propagate like A --> B --> C.
Thanks,
Steve