For my Gaming 7 motherboard, Nvidia graphics card, and Dell 5K monitor, I finally got around to actually following the instructions in this thread by setting these options:
- Windows 8/10 Features: Windows 8/10 WHQL
- CSM Support: Disabled (this doesn't appear unless Windows 8/10 Features is set to one of the Windows options instead of Other OS)
Now my Dell monitor connected to Nvidia using mDP boots into Clover at 4K instead of 1600x1200. The Intel Graphics always booted this monitor into 4K.
It doesn't affect the BIOS screens (version F20), and it doesn't affect the EFI Shell (max console lines is still 60).
It affects Clover and Mac OS verbose and non-verbose boot. I think it affects the Clover debug text for kernel patches, etc. (after you choose to boot a Mac OS).
For the Apple 30" Cinema Display connected to either Intel Graphics or the Nvidia, it still booted into 1280x800 instead of 2560x1600. So in this case another solution is required (maybe the EDID override protocol idea).
The Dell in 5K mode (dual DP) still boots at 1600x1200 into Clover and Mac OS verbose and non-verbose boot. The system crashes as usual when MacOS completes booting (I'm still using El Capitan, haven't tried Sierra). 5K works when it's not connected at startup.