I sign into my work Mac with my personal iCloud account. I use most of the Apple features, but don't sync files. My login account is attached to Active Directory, and admins would have to sign in with a standard local account or their own AD account to manage my device. AFAIK there's no way to access the Photos.app contents from the filesystem. I haven't tried that hard, but you can't look in the directory in ~/Photos. I'm sure at some level most of this stuff is possible, but only in some extreme situation would anyone go that deep to access any of it.

I'm much more concerned about accidentally syncing work things out to iCloud than syncing personal things into my work environment.