i just built a rig with a i9-9900k, moving from a X99 mobo with a 5960X cpu which had 40 lanes vs the 9900lk's 16 - both CPUs have 8C/16T, so i was a little concerned about loss in performance in video editing. I was attracted by the higher clock speed of the 9900k, as the 5960X ran at 4.2 GHz - first test video i did, when i had the 9900k at 4.9 OC, the same file the 5960X had rendered in 41 minutes, the 9900k did it in 27 minutes, so it was a considerable drop in time to render, which is what i was hoping for
i started giving OC frequency more attention when i saw what bumping the 5960X from 3.9 to 4.2 did to render times - not as dramatic as i just described above, but enough to give me some respect for the value of high OC frequencies.
I still haven't figured it out, but the Z390 chipset is supposed to have 20 or 24 lanes of it's own - been meaning to research that.
One warning if you do go with the 9900k - i've had two motherboards and two CPUs RMA'd - the first one, an Asrock Taichi Z390 fried itself the instant i flashed the "latest / greatest" BIOS release, never got past POST on reboot and each attempt got worse until it fried the CPU's graphics side so i had no display. THen i noticed other posters on the web complaining of issues and then one popped in here into my thread stating he had fried his as well. Asrock has pulled that BIOS off their webiste, but point is, that CPU is so new, and power requirements / limits seem to be still getting the wrinkles out. The 2nd mobo, Gigabyte Z390 Aorus Master, was just a quality control issue, the BIOS chip was apparently defective from new and kept corrupting worse and worse
i regret being a beta customer tester, but while the 2nd i9 cpu was running i was impressed. Didn't make it to 5.0 before the board went south.
I can't speak to gaming, as i'm not a gamer
fwiw