Apple has provided testers with seeds for the release candidates of tvOS 14.7 and watchOS 7.6, as it nears releasing the final versions of the updates to the public.
New builds of betas can be acquired by developers in the via the Apple Developer Center, or as an over-the-air update for hardware already using earlier beta builds. A public beta version of the releases usually arrives shortly after the developer counterparts, through the Apple Beta Software Program website.
RC versions are typically the last test version of an Apple software update before they are made available for general downloads by the public. It is likely that the final version of tvOS 14.7 and watchOS 7.6 will arrive within a few days of the RC's seeding.
During their development, the betas didn't seem to reveal any new features or major changes, making them appear to be more a compatibility and maintenance release. Apple is also beta-testing milestone versions of tvOS 15 and watchOS 8, which will ship this fall.
AppleInsider, and Apple itself, strongly recommend users don't install the betas on to "mission-critical" or primary devices, as there is the remote possibility of data loss or other issues. Instead, testers should install betas onto secondary or non-essential devices, and to make sure there are sufficient backups of important data before updating.