Question about Seagate FireCuda 520

If Synology has no reservations, it should work. I use the M.2 for video editing. I can't decide whether it makes sense for your NAS. The connections are important in order to be able to use the data throughput in full bandwidth.

Well, the question is not so easy to answer with a yes or no.
If you run the two NICs in a bonding and have several people actively using the NAS with e.g. VMs or video editing, this can bring a certain benefit. If you only use it with one user as ordinary storage, I would rather rely on reasonable HDD in a RAID5, for example, as this can also fill the 1GBit/s of the NIC.
You would have to describe your area of application a little to be able to clarify the question.