Some memory speed benchmarks with a Ryzen 1700 @ 4.0GHz and a 1080 Ti, 2666 Auto vs 3200C14 vs 3466C14 tweaking sub-timings. Timings and settings used in the comments. : r/Amd
Ryzen 7 2700X Memory Optimization benchmarks vs Core i7-8700K
RAM speed on Ryzen 7 2700x - CPUs, Motherboards, and Memory - Linus Tech Tips