...and only a few months later, I surrendered.
The OWC Express 4M2 is up and running - and it works on both iMac 2019 and 2015 because the latter can use Apple Thunderbolt 3 to 2 adapter and no bottlenecks.
I am very interested in your results with the 4M2 because...
I currently have a "late 2014" iMac 4GHz i7, 32 GB ram, USB 3.0, Thunderbolt 2, and will likely upgrade to iMac pro, maybe next year. I only have a single 256GB SSD inside the iMac, used for applications and rely on external SSDs for storing data, including VI libraries. Currently my external solution is the OWC Mercury Elite dual pro mini enclosure (no fan) with 2 SATA III SSDs.
I need more storage now for VIs and would like to buy faster throughput for the soon to come newer iMac Pro. I am looking at 1) another OWC Dual Mini Pro with two 2TB SATA III drives, no faster than what I have now, or 2) something like what you just purchased and NVMe SSDs. Also looking at:
https://www.bhphotovideo.com/c/product/1381233-REG/dynapower_usa_netstor_na611tb3_thunderbolt_3.html
A backwards compatible Thunderbolt NVMe enclosure would give me faster throughput now with my Thunderbolt 2 iMac and even faster later with a newer thunderbolt 3 iMac. My dilemma is that I can't find ANY INFORMATION on how a Thunderbolt/NVME solution actually improves Logic Pro X performance over USB/SATA III, when it comes to streaming and loading samples. In other words, if my current setup loads a template in 45 seconds with the SATA III bottleneck, how much faster would a Thunderbolt-2/NVMe or Thunderbolt-3/NVMe solution perform the same task?
Any REAL WORLD info you could give me would be helpful.
Thanks