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 and light video rendering, the 6700k or the 7700k is still a vary good option if you can find for a decent price that is, Don't go and spend $300+ on a 7700k when that i5 is $300 if you know what I mean.