What are you using to backup your libraries?
At the house I have a four drive JBOD (non raid) TB enclosure. I have two independent project and library files so I install two SSDs and two spinners One SSD for one project, the second SSD for the other. Backups and archived projects go on the larger capacity spinners.
You don't necessarily need TB3 enclosures for your project as the adapter mentioned above is by directional. With it you can use a TB2 enclosure with a TB3 Macs while providing nearly the same real world drive performance. YIts cleaner with a TB3 enclosure, however.
At the office I have NVMe drive in a TB3 dock, that thing flies.
Generally you get what you pay for in the storage area, and its a bit of money tp play fast. For some of us, time is money.