Updating the BIOS results into default settings. I believe it must be related to any specific hardware I have into my build.
Nevertheless, follow one of many guides you can find in here.
Pascal support is from El Capitan (don't remember driver version, sorry), and following...
My BIOS version is 3402.
Helped me a lot on your booting issue, if it's what I'm thinking, to understand what EFI partitions really are.
Just a FAT32 Hidden volume once mounted you can mess with LOL.
And that exactly is what I did, messing things a little bit ;)
Mine worked with latest drivers without editing config.plist file.
My specs are:
GTX960 4Gb OC, Skylake chipset, running a ASUS Z170 Pro Gaming, 16Gb of RAM, 1 SSD for Windows, 1 Tb hard disk for macOs Sierra.
In my case i went crazy with sound on my ML Install.
But somehow i managed to get it to work by installing VoodooHDA 2.7.6 ML.
Now my installtion is cloned to an USB drive (for safety) LOL
Hope it can help ;)