5 GPU rig PSU

Hello guys,
Not new here but my account got hacked, so i froze and set a new email with another account.

Short story:
Acquired 2 more GPU's for my 3 gpu rig, and also a 12V - 130A (1700W) server PSU, until here everything good, got my psu working, and my cables soldered pretty good there.
I will be using a 200W pico ITX to power a HDD and motherboard/CPU, something entry like g4400 and ram and the Pico ITX is powered from same server PSU.

We are talking about 3 rx570 one rx470 and an 380x so 800W plus 100W from PC? i got them voltage lowered in bios, so i think i wont ever get over 150W per GPU

i think grounds are good if i'm powering PICO itx from same psu that feeds GPU's.

any advice's that might go over my mind?

Also another thing:
i have usb3 pcie risers, and seen that it needs 5V from molex to lower it to 3.3V, went to datasheet for the LDO regulator and max input voltage is 15V so if i inject 12V there should work, but regulators tend to heat up if voltage difference is too much.

Asking here if anyone knows how much the 3.3V line is supposed to consume...