If you're going to be gaming at 4k, it won't make a bit of a difference which one you go with. It's all going to be up to whatever your gpu is - which I hope you don't cheap out on. 1080ti recommended. 1080 can work too, but fps won't be as consistent.
Go with the 1600 non x. Cheaper than 8600k, and comes with a good cooler to boot. The 1600x isn't worth the premium for a minuscule couple hundred mhz more, plus doesn't come with a cooler.