4K at 27" is an unfortunate resolution / density. I know, I also have such monitor :(.
That said, 10-15 fps on X11 is a pathological case, something is wrong there. When I ran X11 and played with xrandr, the slightly larger framebuffer had zero impact (outside games) on AMD Vega64.
That said, 10-15 fps on X11 is a pathological case, something is wrong there. When I ran X11 and played with xrandr, the slightly larger framebuffer had zero impact (outside games) on AMD Vega64.