NetApp NFS and CIFS are configured on a per SVM basis, and both are configured independently of each other. If the checkbox to enable NFS is not visible in the System Manager GUI it is because you haven’t licensed it yet.
You will not be able to enable NFS when creating a Storage Virtual Machine (SVM) if the NFS license is not installed. Although they will typically come as a bundle, each of NAS and SAN protocols are licensed separately.