Developers enrolled in the program can access the latest builds by either visiting the Apple Developer Center or updating their Macs to the newest beta software. For public users, beta versions are normally made available through the Apple Beta Software Program after the developer versions are released.

Release candidates are typically the last builds of a beta-testing process, and usually is the final one before the official release.

The release candidates of iOS 16.7.2 and iPadOS 16.7.2 have build number 20H115.

While Apple hasn't advised what the content of the updates are, it is likely that they consist of security or major bug fixes, or are adding compatibility for new hardware or software.

Source: Appleinsider