Checking reviews of this board and see only one m.2 slot, there are pro4 version with one LAN port and two m.2.Does it works with pcie SSDs?Newer loader should accept m.2 ngff, as synology released expansion slot for those this year.Old loaders/DSMs supported just m.2 SATA spec SSDs.Using cache feature on few production systems.BTW cheap ASM1061 dual m.2 slot sata expansion boards works fine (50$),same as QNAP expansion board dual m.2 SATA (110$) but in has addinional cooling (yep, they are hot when used as cache 50-75C).
Degraded by smart wear level for 30% past 12 month.Consumer grade SSDs (any way its mirrored and capped by SATA spec speed limit, 400MBps +/-)
Off topic ,but maybe someone will find it useful.