I've been using Synology Diskstations, both in business (small business IT) and home (amateur photographer) for a bit more than a decade. (Windows shop so I have nothing to add on the Mac SCSI front)

RAIDS are great, but you should be aware that Diskstation motherboards can fail — and a replacement can take as long as a week. What would you do if that happened? Given your investment in media, it might make sense to buy a second one, leave it unpopulated with media — and you can swap everything over if you need to. You might be able to order a motherboard, but what happens if the power supply fails? (something I have yet to see)

Synology has built-in functionality to keep folders between two diskstations synchronized. It’s not fast enough for separate offices to use for apps that use lockfiles, but it’s fine for making sure you have a working box you can swap everyone over to if there’s a disaster with the primary one.

Personally. I manage off-site storage this way: Diskstation in my basement, synchronized with one at a friend’s house. Synology has a way to encrypt synchronization data over open lines, but we both have pfSense firewalls, and a VPN tunnel.

Also you’ll find a way to backup your data to AWS. The cheapest way to store data online is AWS Glacier, but the mostly-write properties of Glacier manes incremental backups problematic. I’d backup to AWS, then sweep into Glacier as it seems appropriate. I do this as a business backup solution.