i would start by getting one then two cards setup and plugged into the motherboard not by risers and then add the others one by one

60gb will start windows. you will need more space for the virtual memory
on a 6 vega and 1 rx480 rig, system information shows 50gb virtual memory is being used out of 120gb available

the risers i binned have a light blue pcie connector ver 002

do the cards light on system start or when there first detected by windows?