Gonna build a Threadripper, seems like I'm gonna wait forever to get an AMD specific 64 GB memory set for the thing, like 64 GB G.Skill Flare-X... think I will just pull the trigger.  There is some fast Trident-Z mem in stock I can get.  Could really use the extra horsepower now rather than wait.

Soo, if I understand XMS correctly, it's just an alternate profile stored on a chip in the modules for easy setup for the factory overclocked speeds.  If I go in and set it all manually - speed, timings, CAS Latency, and voltage the end result is the same?

Correct. With xms at least you know the memory is certified to run at those settings/timings. You can run the profile or set it yourself manually if your motherboard provides you with all the settings to modify