After iOS 12.1 beta 2 Apple released the second beta version of macOS Mojave 10.14.1, watchOS tvOS 5.1 and 12.1. The updates became available only for registered developers.
The main innovation macOS Mojave 10.14.1 and watchOS 5.1 is the ability to perform group calls on FaceTime. This same feature has appeared in iOS 12.1 after it was removed in one of the latest beta versions of iOS 12. It is expected that group video calling on FaceTime this time, I am not going anywhere and will be available to users after the release of the firmware.
As for tvOS 12.1, then this update is purely technical. No serious innovations in it was observed.
Registered developers can install macOS Mojave 10.14.1, watchOS 5.1 and 12.1 tvOS right now via the standard update mechanism, Apple.