So, if you connect a non-4k display, the Mac will render in a way that won't look as sharp as the display could. That's not true. A display will happily utilis

So, if you connect a non-4k display, the Mac will render in a way that won't look as sharp as the display could. That's not true. A display will happily utilise it's full hardware resolution. The problem, as I understand it, is you can't change the DPI of the monitor. You can configure a 2560x1440 display to use a lower resolution (e.g. 1920x1080 or 1600x900), but then the monitor itself will upscale this into a blurry full screen. Tricking MacOS to change the DPI would let you configure the display to use all 2560x1440 pixels, but drawing everything bigger, at full resolution.