AMD threadripper like Ryzen will require a special kernel so for now not supported. I have Ryzen working but we are waiting for a High Sierra kernel to move up to that software.
Intel X series i9 latest generation were announced by Apple for the new Mac Pro, however from reading the testing threads these are not yet working either.
If you want something now that is working the i7 7700k IMO is the top contender for all around performance and compatibility especially in Sierra and High Sierra.
If you need extreme compute for multi thread apps then wait a little for the i9 support and testing, Threadripper is a gamble as some apps work great and others are spotty on the Ryzen systems at the present time. Nvidia web drivers are also an issue with Ryzen right now, the web drivers are not at full performance as with Intel systems. For the price they can't be beat for multi core work but the i7 7700k is close in multi thread work even though it has half the cores and in single core functions it can't be touched.
Ryzen single core = 4200, multi core 25,000
i7 7700k single core 5500, multi core 22,000
i9 and threadripper will have better multi core scores but getting the bugs worked out wil take some time. If you can wait for an i9 system they will eventually be figured out and thread ripper will get a kernel eventually as well the Ryzen kernel may actually work but since app,e doesn't use these CPUs Intel always has an edge for reliability and ease of instal and updates.
Ryzen, threadripper, and i9 for now = experimental
i7 7700k, i7 6700k are working great and = supported
Older xeon chips will work as well but buying older equipment may not be good for future proofing your setup, i.e.. ddr3 ram m.2 @ 8gb/s versus the newer 32gb/s USB3.1 etc...