Yes, you can use M.2 NVMe SSDs in slots 2 & 3 either as additional high-speed data storage or as a read/write cache for your SATA HDDs. The choice depends on how you configure your NAS OS (TrueNAS, Unraid, etc.).
Slots 2 & 3 run at PCIe 3.0 ×1 (830 MB/s).
Slot 1 is faster (PCIe 3.0 ×2).
So, flexible but not the fastest NVMe speeds. Perfect for caching or secondary fast storage.
