Dual PSU, USB 3.0 Powered Risers - Correct way ?

Hello to everyone in this forum. I'm new to mining world. I already have one rig with 4 gpus with one psu. All works great.
I have a question for dual psu setup. I ordered some components and planing a 6 card rig with dual psu.

So my question is just to be safe, what is the correct way of powering this rig.
I was thinking >
1st psu connected to mobo, cpu - 3 gpus and 3 usb 3.0 powered risers ( so 3 gpus be powered by same psu via risers and 8 pin)
2nd psu connected to 3 gpus and 3 usb 3.0 powered pcie risers.
Also i will be using add2psu adapter for connecting both psus

I assume that 3.0 powered cable is not transferring any power to mobo. only data? Also don't see any logic there why should power been transferred via usb from mobo.

I read alot about it and some say that 1st psu should be connected with all powered risers and and mobo, and the second one with gpu-s. but i dont see any logic there, that sounds that im powering one gpu with 2 psu, and i dont like that at all.

Just to be clear am talking about 2 x 750w evga bq and 6 x rx 470 gpus

Correct me if im wrong with this

Thanks in advance