Ive just got a Gaming 3 with a 950 pro - also having issues. I managed to get the 950 pro to show up in the Boot Options by clearing the CMOS and then "loading optimized values". 950 pro then showed up, installed win10 via DVD, all good. I installed the samsung NVM express driver, performance in Win10 is superb.
However, when it comes to booting.... takes an age to boot.
I get the normal boot logo for a couple of seconds, then the screen goes black with a flashing cursor top left, pauses for 10secs, then I get the windows flag and spinner for another 20secs, then it boots to windows.
Previous mobo (also GB) booted in about 7secs using an 840 pro on normal SATA.
Ive updated to F4 bios, 950 pro disappeared again, clearing CMOS again got it back, but poor boot performance is still there.