I want to know the highest resolution available (in HorizontalxVertical pixels and refresh rate) with normal desktop usage (editing code). Either over HDMI or DP.
Sometimes the desktop resolution is limited to QXGA (2048x1536) over HDMI, or QHD/WQHD (2560x1440) over DP. But the video resolution goes up to UHD/4K (3840x2156) due to codec compression / decompression. And then the SoC manufacturer only specs the video resolution, and maybe mentions QXGA as a secondary (without the numeric resolution). Which is then (understandably) copied by every blog and SBC manufacturer out there.
But one of your competitors describes the RK3399’s display interface like this in its hardware user manual. Note the difference between HDTV and graphic display resolution. 4Kx2K vs QXGA. :
RK3399 support HDMI 1.4 and 2.0, up to 10-bit depth color mode, up to 1080p at 120Hz and 4Kx2K at 60Hz HDTV display resolutions and up to QXGA graphic display resolutions.