not sure how i came to 4 x1G ports for the 1621+ but there seem to be 2x1G and 1x10G port, so its not that bad after all
maybe synology will have m.2 nvme usable as normal data volume later with 7.0? qnap does support that (and even more) so they need to move or people will not consider them for a new unit anymore, 2 slots in the unit and 2 more as pcie card might be ok