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 2700X RAM Speed Test - YouTube
DDR4 Memory Scaling Performance with Ryzen 7 2700X on the AMD X470 Platform - Legit Reviews