I have the 2015 17 with the 4k screen. Provided you are sitting about 2 -3 feet from the screen you can not really notice the bilinear blur associated with 1080p scaling because the pixel density is so small.

So, unless your eyes are absolutely perfect I wouldn't worry too much about it. Its never going to look as crisp as native 4k but it looks far better than any kind of scaling on a lower DPI screen.

I played Battlefield 1 for ages on my 17 R3 at 1080p and have the 15R3 4K now. I have noticed it looks a little blurry when playing it but the 1070 gives off great performance