SeriousGaming101 :
Overclocked 2700x CPU by 20% = 9900k base performance?
The 9900K is anywhere between 5% to 20% faster depending on the application or game. This is also dependant on what stock actually means. Stock for the Z390 motherboards tend to mean a slight out of the box overclock whether you like it or not. If you are running the 9900K with MCE Multi-core enhancement enabled on the Z390 then it will be running a lot faster than stock.
If on the other hand you stick to the 95w TDP limit then it is very close to the 2700X and only tends to lead in games...with applications very close though overall still int he 9900K's favour..but at the price that is not really a win!! Though let's be honest, who buys a 9900K to run it at stock 95w TDP?
The 2700X does not really have any overclocking headroom and an all core overclock stalls at around 4.1 to 4.2GHz and funnily the XFR auto overclock tends to do a better job of overclocking.
Finally, if you do get a 9900K and good enough cooling, then it can do 5GHz all core and then it is one hell of a CPU though again badly loses out on price to performance....
For a balanced CPU the 2700X is overall much better especially if you are gaming at 1440p or 4K...If on the other hand you want high refresh rate gaming and maximum FPS then anything from the 8600K through to the 8700K will pretty much be on par with the 9700K and 9900K...Pound for pound the 8700K is the best option if gaming is the primary focus....
I should also have mentioned the performance across workloads like editing, encoding, decompressing etc also apply in the same way with the 9900K coming out on top if allowed to run with MCE or any sort of an overclock where it will be better, though price to performance it loses out big time....