For a start, the M.2 NVMes on the Synology can only be used for read/write caching performance benefits, whereas the slots on the Terramaster can be used for caching AND raw storage pools (i.e to store data the same as the HDD bays). Both systems support the choice of BTRFS or EX...
Underside of the enclosure is where you'll find the two passively cooled M.2 2280 NVMe SSD slots intended for caching purposes, these cannot be used for storage volumes. Installation is simply a matter of removing the vented cover, insert a drive and gently push down to secure — no screws...