Well I didn't enabled anything in bios before windows setup but I've made bootable usb with Rufus, GPT partitioning for UEFI systems, so I assumed that it'll for sure be UEFI.
Only thing I've changed in bios was 4g Enable, because it was disabled by default, and 3 of my cards was with yellow triangle in device manager, switching 4G solved it, but during some boots not all cards are again found by OS, and they appear as Unknown VGA Device on Unknown Device's list.
Really don't know what I've messed up. Maybe PSU draw offset is too low? It's 1600W, even when counting efficiency on 100% load it should be minimum 1350W (85%).  Dont know how much Zotac and Asus draws at 75% tdp but MSI was ~210w on skein/ea so I've just distributed them 2 on one psu with mobo and cpu, and 3 on other alone.