I don't think you understand how resolution works.Your monitor is 1920x1080, the exact resolution of 1080p video. This means every pixel of the video has a pixel to fill on your screen.Loading a video in 4K does not magically quadrouple the amount of pixels in your screen. To fit on your screen the video has to be scaled down so that it loses enough of its pixels to fit on your screen, meaning blur algorithms have to be enacted to average an area of pixels into one pixel. This would actually decrease the quality of the video over raw 1080p.
That is awesome, but would anyone happen to know what settings to render a video to get 4k?
Could you restate that a bit more clearly? That question could be taken two ways.