I am using Lightroom 6 and 4K monitor.
My cMP 5.1 also has Highpoint SSD7102 installed.
Booting with NVMe SSD hardware Raid0 does not make Lightroom run faster, it feels similar to sata ssd.
It seems that the larger the 'Lightroom Catalog.lrcat' file, the slower the operation speed.
Now my 'Lightroom Catalog.lrcat' is about 14GB and 'Lightroom Catalog Previews.lrdata' is about 160GB.
Using a 4K or higher resolution monitor will make the catalog file grow faster.
The recommended thing to do is to store the Lightroom Catalog file on a faster SSD, maybe your Highpoint SSD7101a, but the improvement should not be much.
Using smaller catalog files improves speed and is cheaper.
I think using the fastest single-core CPU, and more cores for export, is the way to speed up Lightroom the most.
What CPU should Mac Pro 7.1 use to help Lightroom speed up the most?
Lightroom 6 is pretty old; they're on version 9 now. Lightroom is definitely faster with a smaller catalog, but that can be pretty limiting to chop up your photos into multiple catalogs. There's also functions that are completely unrelated to catalog size that are slow--for example, the clone/heal brush and the adjustment brushes. Part of it is the way the whole application is architected such that you can go back to the original unedited photo, with retained history, and part of it just appears to be a lack of interest in speeding up performance on Adobe's part. For many functions it uses only one a few cores, even as processors have moved to having many cores--and that's clearly the direction of future processor improvements as well.
Because it is dependent heavily on CPU, having as fast a CPU as possible does help, but now with the enhanced GPU support in version 9.x a fast GPU with plenty of memory also helps. Some testing I've seen online suggests that LR seems to rarely use more than 6 CPU cores, except for certain tasks like exports, and Adobe's own hardware recommendations seem to imply the same. That said, for exports, more cores are definitely used. Other tasks like raw decoding are tied to the speed of a single core, as it's a pretty linear task that isn't able to be parallelized with most raw formats (Sony's format is an apparent exception, but I don't know if Adobe leverages that or not).
I ended up choosing the 16-core processor in my Mac Pro as a compromise. The 12-core would be another good choice. Both support the higher 2933Mhz memory speed, and have plenty of speed. While the base is 0.1 Ghz higher on the 12-core, I have found that the functions that tax the CPU spike it up to the 4.4 Ghz maximum anyway, so that base speed is pretty much irrelevant. I often have multiple apps open and running, so for me the 16-core option was better as I could be assured of resources for the other apps.
If I wanted to buy a machine 100% purely for Lightroom use, right now Apple doesn't have one, at least until they update the iMac line. The i9 and i7 Core-X processors perform extremely well with Lightroom, and have very high clock speeds.