MicroOS and its derivatives are all based on Tumbleweed. MicroOS was intended to be used for container workloads. Aeon grew out of that with a GNOME desktop, Kalpa a KDE desktop. Because they were focused in a way Tumbleweed is not, they are a more opinionated distro. On the other hand, Tumbleweed is a rolling distro that wants to be all things for everyone.
I guess you get the atomic system, but with Tumbleweed you get snapshot backups anyway.
One of the main advantages of Tumbleweed is the extensive testing pipeline. I'm not sure how a derivative would be able to offer a similar experience