Performance is maybe a per cent or two higher than we would have expected. The combination of 3,200MHz frequency and CL16 plays well on our overclocked Core i7 test platform.
Of course, you are not going to see huge differences in performance with a cache-heavy CPU and high-end graphics card (Gigabyte GeForce RTX 2070) in situ, but it still makes sense in opting for DDR4-3,200 memory as there's only a small price premium for it over and above 2,667MHz stuff.
With respect to overclocking, we managed to run the standard timings at 3,600MHz by bumping up the voltage to 1.45V. There's nary a performance benefit outside of synthetic benchmarks, however.