Up until a week ago I would have suggested the UniFi. Since the latest snafu, the handling of the breach not the breach itself, I’m not so sure anymore what would be the best alternative. Perhaps just their EdgeRouter devices or a mikrotik device.
Also, the security report you're talking about came out like two days after a huge blow-up on this site because of a report they added advertising to a UI for one of their products. (The controller I think?)
Its muddy right now, I run Ubiquiti EdgeMAX switches and EdgeRouter at home, but I wouldn't recommend them right now (see another comment of mine, or check out the subreddit), for NAS I run TrueNAS, on a home built server.
For the Mobo I suggest finding a decent board (AMD based one if you want ECC RAM) and then use a PCI-e controller card to support the hard drives you need. It is hard to find a nice MB with all the SATA ports you need, using an external card gives you a lot more options. When I researched it everyone recommended an "LSI Logic Controller Card LSI00301 SAS 9207-8i" (eg. https://www.amazon.com/LSI-Controller-LSI00301-9207-8i-Inter...) and it has performed very well for me. If you go that way you'll need a SAS to SATA cable, they are easy to find as well.
I wanted to do that for a while now. Do you happen to have a good suggestion regarding whose products are worthwhile?