I've been running the OWC miniStack STX with one 2TB NVMe and one 2TB SATA SSD for months now with my Mac Studio, and it has been flawless and running 24/7 without a hiccup. The NVMe drive speed gets about 700MB/s read and write. The SATA SSD is actually connected as a USB device and gets in the 500MB/s range. I also have every port in use, including running an OWC Envoy Express 2TB NVMe, off of one of its ports (which gets about 1500 MB/s read and write).
As long as you aren't looking for maximum sequential speed, then this is a pretty good choice. IOPS are really good, and more important to me than max sequential speed. Running Thunderbolt is much better than USB for external SSD storage, in my experience. Trim is supported out of the box and all of my disk utilities can read the SMART status and temps off of the drives natively.
Perfectly sized to seamlessly stack with the Mac mini and the ideal storage and connectivity expansion companion for Thunderbolt or USB-equipped computers.
eshop.macsales.com
OWC miniStackSTX Internal NVMe:
OWC Envoy Express External TB3 Enclosure: