Adding to the discussion again.
Upgraded from a 970 EVO Plus 1TB to a 2TB 980 Pro in a JEYI Thunderbolt 3 enclosure. No real change in read speeds but doubled write speeds. Not too surprising as the enclosure is only PCIe 3 - not the PCIe 4 the 980 supports.
Interestingly in system info under NVMExpress - all the specs match the numbers of the internal Apple SSD of my 2019 16" MBP.
EDIT - Ran AmorphousDiskMark and got R 2851 / W 2782 with the 980 Pro.
Also tried an official Apple cable and one I got from Ali and speeds were similar - not all cables are created equal but looks like I got some cheap ($US29) good cables.
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