Wut? 1070 Ti? Lol, 1080Ti/2080 is the minimum for 4k 60FPS! Everything below will never give you average 60FPS in 4K, not even talking "constantly 60 FPS".
1070Ti would push 60fps only in some indie game, or 10yo game.
2080 Ti is way to go for constant minimum 60 FPS at 2160p.....and even that thing manages to drop down at ~59FPS level, rarely though.
And yeah, for 60FPS u don't care about CPU horsepower, while it has decent clocks, pretty architecture and >=6-8 threads - because game devs unoptimize games for 6-8 threads lately, some 4core i5 that was decent 3 years ago, is decent no more. IDK why it turned out so quickly - maybe because of core race back again...