Lawrence Finch wrote:
Not a separate Apple ID - a separate device.
Both.
Beta software can potentially render a device or a Mac unstable or unusable, can potentially corrupt associated local data, and can potentially corrupt associated iCloud data, or can potentially convert the iCloud data into a format older versions cannot access.
Do not run a beta with any device or any Mac needed to work and work reliably, with any data needed available, and with any Apple ID and any associated iCloud data needed available.
If you aren’t able and willing to “nuke and pave” — to perform a factory reset and re-install with no restoration — after something goes badly weird with an install or with iCloud, don’t run a beta.