So for 1080p 60FPS a gtx 1060 6gb is perfect for this for the GPU.
If you want windows 7 then the best you can get is a 6th gen intel skylake which is a very poor use of money at this point (paying the same for less CPU). Ryzen and 7th/8th gen intel will only work properly with windows 10
Why does it have to be windows 7.