If we look at these three features separately:
Daily backup of a specified folder → Will it be backing up from one computer or multiple computers to the NAS? (Both are possible for us.) Besides overwriting when there are updates, if files are removed from the PC, should the files also be deleted remotely, or should they be kept?
Public network access for simultaneous use → Is it read-only, or is writing also allowed? Is this referring to sharing via network neighborhood SMB? Sharing with macOS and PC?
Access outside the company → For mobile phones, access is possible via an app, and for PCs, we provide VPN or a web interface for connection.
You can first consider the details of these requirements, and then we can provide corresponding configuration suggestions.