there is also another seller on ebay that has a lot of the 9a3 3.84TB ssds in stock. They are not optanes but seem to be a good all round drive for a good price. if you are still considering the samsung pm1735 pci, cdw has them in stock for $489 but that is for the 1.6TB. even though your mb has a lot of x16 gen4 pci slots, I would be hesitant to use them on only a 1.6TB drive.
I am confident that I have 4 drives by the end of this month. More likely 8 or 12 even. Might as well become one of the bad boys and sell PM1735 3.2TB at sick prices. I am actually quite positive on the PM9A3 - the U.2 versions seem to be a steal: price and performance wise.
It might be more interesting to do what I did with a similar mb and use the highpoint 7505 nvme raid controllers with 4 x m.2 nvme gen4 drives. it is a good way to fully utilize at least a couple of the x16 slots!
I am not a fan of your highpoint cards at all. Frankly I am quite sceptical about them. Thats exactly why I am glad that you are also testing, simply since opinion is one thing, testing is another. I am all in for M.2 drives for OS partition or so. But I doubt those M.2 as hot storage or even hot cache.
If we are talking about normal RAID controllers for U.2 drives etc... by then I believe the time for hardware RAID controllers is over or is soon over. Again thats why I am so interested in these tests. ZFS is imho ill-suited even though it has a huge fanbase. Just because ZFS is a monolithic approach to filesystem and storage. Monoliths are destined to fail on the long or on the short run. MDADM, RAIDIX and more are imho the future. Granular control, higher flexibility, no artificial/secret drive standards for recovery,... instead a bunch of devices you can just plug in to another system and given the current driver it just works with minimal effort. Also this enables a whole lot of optimization and control, which a RAID controller does not. Apart from that, RAID controllers are a SPOF too. Nothing bad by getting rid of them if performance and reliability dont suffer.