Depends a lot on your CPU's architecture as well as workloads, how far ahead it prefetches vs how often it's stalled on large memory reads. So it's hard to know. e.g. Zen+ (Ryzen 2000) was seeing 10% in some gaming workloads going from DDR4-2400 to DDR4-3600, but it's much less drastic on Intel CPUs or even Zen 2 (Ryzen 3000) because the memory controller is smarter so the slower RAM is less of a detriment. And then if you go above 3600mhz (or 3800mhz if overclocked) on zen 2 you start getting negative returns for a bit because the CPU memory controller can no longer run at the same clock as the memory and that induces overhead. But maybe a 4800mhz if it can be stable easier gets far enough ahead of that penalty that the improvement goes positive again. Or maybe Zen 4/DDR5-lake just works with memory entirely differently and the performance gains are massive or neglible.

The short of it is it's very hard to make predictions here.