Hello Don
We recognize your desire for more precise answers to licensing-related questions; however, we recommend consulting a Microsoft licensing specialist for inquiries of this nature.
For the three users connecting through SMB file sharing, you do not need RDS CALs. RDS CALs are specifically for remote desktop sessions, not for file sharing.
RDS CAL allows a user or device to connect to Server specifically for remote desktop sessions. It grants the right to access the server's desktop and applications remotely. Windows Server CAL permits a user or device to access the resources and services provided by a Windows Server, including file storage, printing, authentication, and more. It's a broader license, not just remote desktop access.
Please ask one question per thread. For additional questions, consider starting a new thread. This helps ensure you get clear and helpful answers.
Thanks,
Karlie