Please excuse my rambling post following:
I like that drive but I do not run a boot drive on my 7101A-1, and I am uncertain of the benefits for doing so in comparison to running off a SATA SSD drive (which is what I am doing now). I've thought about testing the benefit by removing my RAID and trying the boot drive on one of the slots, using one of my two 2 TB drives, on what would be an "was-RAIDed".
I also read somewhere that there is a particular slot on the 7101A-1 that is better cooled, hence better for the OS. Although I am also unsure if an OS would need more cooling than if the drive was being used for video work, which IMO works drives harder than an OS.
Also, I wouldn't be worried about the sector size. It's performance that counts, and these drives are far more complex than just sector size. Although a note about performance - in the future, type 4 drives - which can benefit from PCIe Type 4 slots - will eventually become the norm. I've also read here that the Western Digital SN850 is very fast on our setups - as would be the Samsung 980 Pro (presuming the Samsung will work as it should on our cards). But those solutions are pretty costly IMO.
You're good brother, I'll elaborate -
It all depends on one's use-case scenario - for me, the iops and faster 4k reads/writes do matter as the performance difference is not negligible when comparing NVMe to Sata SSDs for OS and other uses or Apple PCIe drives to non-4kn drives, it just can't be ignored especially if one is trying to squeeze every bit of performance out of these old machines.
I also posted about the middle slots getting better cooling on the 7101A, which hasn't changed, so I keep the OS and other heavily used drive installed in the middle slots while Windows and TM are installed in slots 1 and 4 (outer slots)
This will probably be the last upgrade to the cMP before moving on to a new apple silicon Mac Pro.
I look forward to your feedback on the P31.
Cheers