It appears that only one PCIe 3.0 lane is wired through to each of the four NVMe m.2 slots, limiting the benefit of higher-performance drives. See the first-page block diagram of this schematic PDF for the NAS breakout board:
https://wiki.friendlyelec.com/wiki/imag ... 09_SCH.PDF
https://wiki.friendlyelec.com/wiki/imag ... 09_SCH.PDF