DAS for MAC
Existing system is MacBook Pro (Retina, 15 inch, Mid 2014) processor: 2.2 GHz Intel Core i7; memory: 16 GB 1600MHz DDR3; flash storage: 251 GB running macOS Mojave 10.14.6. Automatic Time Machine back-up to AirPort Time Capsule and separate Back-up to Backblaze. I am considering the addition of external hard drive to move iTunes and photo library off the Mac. Looking at OWC Mercury Elite Pro Dual Performance RAID Enclosure USB 3.1 Gen 1 with two 2 TB WD Red or Red Pro drives formatted either Mac OS Extended Journaled or APFS. Comments or suggestions?
OWC Mercury Elite Pro Dual Performance RAID Enclosure features USB (5Gbit) and Thunderbolt2 connections. Connecting via USB would not be the best choice if you need fast backups because it is half of the speed of TB2. Unless speed is not an issue.
But generally external enclosures even with RAID compatibility will work with your MAC. I am not sure I would pay extra to get NAS drives. Simple WD Black or Blue would do the job just fine.
I hope this helps.