I would recommend leaving it alone.
Staff refers to all non-admin users of your computer and I believe everyone refers to users on your network if you have sharing on.
The files inside my Documents folder seem to be 755 (rwxr-xr-x).. user has full perms while group and other have read-only perms. This is how it should be.
I think the iCloud Drive folder in Finder is a smart folder. The location is actually ~/Library/Mobile\ Documents/ and if you ls that location in Terminal you'll find many folders that aren't visible in iCloud Drive in Finder. The Documents folder is ~/Documents but it appears in iCloud Drive in Finder - which leads me to believe that Finder does some weird magic when displaying the contents of iCloud Drive.