RAM speed: 2666Mhz or 3200Mhz

Yes... but in case of 64 Gb, one manifacturer propose two products; 64GB Kit (2 x 32GB) DDR4-3200 SODIMM and 64GB Kit (2 x 32GB) DDR4-2666 SODIMM. The Problem is: the 3200 making sense or the PC Works in the same way?

Go ahead and experiment if you can afford it. Problem is that the higher RAM speed won't help you as you can't change the BUS speed.

Thanks Mayer. Maybe are good for who experiments the overclocking, sure different to turbo-boost. In Macs this more speed remain unused.

@pl004 - Different markets! Overclockers mostly understand the mechanics of their system. Mac users depending on Steve's famous phrase: It just works

While Apple presses performance it isn't always the faster system when you put them side by side a similar CPU'ed system.. Thats not to say the Mac is a slow poke! just not the fastest! Sometimes they surprise us! Apple was the first to leverage PCIe/AHCI & PCIe/NVMe drives! And then the T2 driven flash chips design which beats 4x PCIe/NVMe blade drives. Only in a Mac Pro can you beat the T2 using Sonnet’s M.2 4×4 PCIe Card brings absolutely ridiculous SSD speeds to Mac Pro If Apple can get off the Intel bandwagon to AMD then we should see some real performance without the heat!

Thanks Dan. MacPro are my dream ;)