Record 4K Lossless quality with Bandicam
This video's shows it's not that difficult to record in 4K resolution at 60fps. What you need is a beefy computer with a fast drive. I suggest you take a (big) ssd which can write up to 600MB/s, or you put 3 or 4 regular drives in a raid 0 array. This is what I have done with 4 WD 1TB drives, giving me a write speed of 640MB/s.
This way of encoding takes the least toll on the CPU, because recording uncompressed means no encoding at all. You only need a fast drive. This means all the CPU power can be used for playing the game.
In september 2016 there are not many videocards which can game you 4K gameplay at 60FPS. If you really want to record at 60FPS in 4K you need a GTX 1080, or you put 2 GTX 1070 or 2 GTX 980ti in SLI.