NAS optimized is the meaning of the standard preconfigured SVM there is ready to use. You can modify the exisiting preconfigured SVM for SAN or Delete and create a new one.
Preconfigured is the meaning of: The cluster, licenses, aggregates, Storage Virtual Machine (SVM), and logical interfaces (LIFs) are preconfigured, and the optimum storage efficiency and performance parameters are set.
You can read https://library.netapp.com/ecm/ecm_download_file/ECMLP2508918 for new SVM or modify existing SVM.