Is your intent to run the display "pixel for pixel" (full resolution), or in HiDPI mode (as "4k on the Mac" is usually run) ?
For "pixel for pixel", you're probably going to want at least 40-43" display size, otherwise text and perhaps graphics as well will appear "too small" in native resolution.
For HiDPI, a display much larger than 27" will produce text/graphics "too large".
My opinion only.