If I'm not mistaken, the smbd full disk access is turned on automatically when SMB file sharing is turned on.
It's not, as noted by many people here. I think it was put into Full Disk Access on my Mac, but it wasn't enabled. When users here noted they could no longer access their Desktop, Documents, and Downloads over SMB, I looked for smbd in Full Disk Access and enabled it to check. I have had to explain to others where to find smbd in order to add it to Full Disk Access. It is completely unnecessary for normal file sharing. It is only under Ventura that the privacy settings prevent seeing folders in the Desktop, Documents, and Downloads folders without user permission. The SMB daemon does not ask for access (at least as far as I could tell).
The way we had implemented SMB on the file-server was through user R/W access to select folders and drives specific to each user. Our file sharing is activated only on the server side and not the client sides. On the client side there is no smbd daemon running.
ll clients were Mac OS Ventura (Intel based) and the server was Ventura (M1 based) as well.
If you use Sharing Only users, you can configure specific permissions for everything within the File Sharing Settings. If you create real users on the Mac, when they log in via File Sharing, they will have whatever permissions they would have if logged in directly. The File Sharing permissions do not override those.
There are times when File Sharing creates ACLs for the folders, and those could possibly override the normal user POSIX permissions.