You would be better off with a separate NAS... It is safer (e.g. a PC crash can still wipe out the SSD data). The NAS can be a RAID 5 for speed and redundancy and shut down when not needed. Also, should your PC get infected with Malware or worse, Ransomware, the disconnected NAS will still preserve your data.
I backup my data to the NAS weekly. As a precaution, my internet access is always disconnected during NAS operations. Granted, a NAS can be expensive but the capacity is higher. Bit of advice, when calculating the storage capacity on a NAS, always double what you need. You will be surprised at how fast your storage space disappears. My NAS was configured with four 4TB drives with a net space of about 10.5 TB. I used up all that space in a couple of years. My NAS is now configured with 16 TB space.
Another advice, buy a NAS with six or more bays. You don't need to use all six in the beginning. But it is easier to add hard drives in empty bays than replacing all four drives in a four bay NAS.