Below is a screen shot of the CPU-Z captured with CPU multiplier set to 41.5x. In fact, for overclocking, the Ryzen 7 2700X gets up to 80 deg C easily and it isn’t stable at 4.2 GHz. 4.15 GHz seems to be a sweet spot for all 8 cores to run at.
As for Ryzen 5 2600X, the same overclocking is done within BIOS and temperatures seems to be fine since it has only 6 cores at 75 deg C. It is relative stable in 3D mark benchmarks but failed in Cinebench R15. We have to reduce it down to 41.5x for stability.
CPU-Z multithread benchmarks
As we can see the Ryzen 7 2700X when overclocked is way higher but it seems to be on par with the Ryzen 7 1800X. When overclocked to 4.15 GHz, it scores 4842 which is a big boost compared to the earlier Ryzen.
The Ryzen 5 2600X, when overclocked scores 3902 and 3689 at default. It scores better than a Ryzen 5 1600X but Ryzen 7 1700 seems better.
When compared to the Intel Core i7-8770K, the Ryzen 7 2700X (4542) is way ahead of the competition (3971).