What impact does updating one Mac to Ventura and not others have on shared data like iCloud or Mail?

[EBW]

This may seem like a weird question but has anyone noticed any issues with having updated a Mac to Ventura that shares iCloud data with a machine that is still on Monterey?

 

[Mike Boreham]

This may seem like a weird question but has anyone noticed any issues with having updated a Mac to Ventura that shares iCloud data with a machine that is still on Monterey?

If you create a Shared Photos Lib on the Ventura Mac, it (and any photos in it) will not be visible in Monterey Mac. Apart from that I don't know any issues.