This is a fairly easy one. The Ryzen 5 2600X does not have any real overclock headroom. However, if you notice your clocks never even reaching the advertised 4.2Ghz clocks then this is for you.
In your BIOS, probably under CPU overclocking, set CPU offset voltage of -0.1000V . That’s right, MINUS 0.1000v
Now you should see the CPU regularly boosting up to 4.3Ghz and your benchmarks should be improved.