At 1080p, the numbers of the fps metric and performance graph are the perfect sice. But at 1440p, the numbers become hard to read. And at 4k, it's barely visible. I don't have a 8k monitor but I imagine that the Numbers would be pretty much nonexistent. I would suggest a setting like the one for the interface resolution, so that the sice of the numbers is not dependent on the screen resolution.
but that just downscales the gui and makes it ugly (because of low resolution), they should add gui size slider (like 25% to 500%)