oskarmp :
Will i5 6400 bottleneck GTX 1070 x 2133mhz in 2560x1080 144hz????
Short answer is: Yes.
Long answer is it won't matter because your video card is also not really up to 2560x1080 at 144fps (144hz). There are few games that require beefy CPUs. Games like the civilization series, GalCiv, and heavily modified fallout/skyrim games, GTA, BF1 as well as a few others are going to ask more of your CPU than it can deliver. With little tweaking and being able to live with less than 144fps your games should look good. If you run everything at max and don't have g-sync then it will be jerky, stuttering, and other issues in many games, perhaps even the majority. Older games are generally less demanding.