we recently went through all this pain (HiDPI) support with our own software. It’s very troublesome.
But if you have a 4k monitor and you’re running it at 200% scaling, you’re seeing everything the same size as if you just ran it at 2k resolution, except you’re getting the OS to do a LOT more work. 4 times the number of pixels, 4 times the video memory use, anti-aliasing computation etc etc.
There’s an argument to just run it at 2k. I doubt you’d actually see the difference, but the load on your system would be greatly reduced.