Back when I bought my x99 system, I wanted and needed 6 cores and 12 threads, I could use an 8 core but wasn't paying the price they wanted, and AMD all they had was the FX stuff. The only platform to get a good performing 6 core was the x99, at the time there were no main stream CPU's that offered 6 or 8 cores.
Now that AMD and Intel both have main stream 6 and 8 cores that perform well, x299 seems vary poor decision for gaming or even video editing in many cases. I would avoid x299 unless your in need of something that x299 supports, All round good performer would be the i5 8600k, $300 USD, and 6 cores which would easily perform the same as the 8700k in games and will still do vary well in video rendering and editing.
Just gaming...