I have both i7-8700k and ryzen 3600 and I have better fps in ryzen rig.
Csgo wise, new ryzens give the best possible performance, other game it's on par or 9900k leads by 5%
What's wrong with the 9700K?
I was just looking at cost and for the 9700K I could get a cheaper mobo that still have the best chipset for cheaper than the top chipset for the 3700X, so the total costs seem to be about equal.
PCIe4 is currently completely useless, even PCIe3 is kinda useless(you get %98 of a RTX 2080's performance by using PCIe2 instead of PCIe3...) - and basically no devices support pcie4 right now anyways. Also Z390 doesnt support it either. Good luck man
300 - 500 depending on settings, 32gb ram bit overkill unless you're doing heavy video editing , running vms or will have a lot of applications open.
better to run 2 x 8gb in dual channel with a higher speed