I am using a 16GB kingston USB3.0 stick with Hive OS on it and it works great.
The 3 molexes on the MB are not connected, I have powered risers (2 per cable coming from the PSU).
Risers are something fishy, sometimes have to switch either cables or power them from another PSU until everything runs fine.
If they have an issue with power the MB shows multiple slots in red, its just figuring out which one to change PSU then and everything is green again.
Which version riser are you using? I use strictly 006c ver and oddly have never even gotten a bad one, yet. I strictly use 120gb ssd, they are $48. I run win 10 Pro, updated to 1709 and Asus bios ver 1001. The 3 molexes are NOT connected on my m/b. I have two sticks of 4gb memory pc2133.
I use 006C risers.
8pin from psu to 8pin/6+2pin (8pin to gpu and 6pin to riser).