If that scenario is possible, how should I wire them? 1 PSU is wiring the 6 Pins and the Satas of the 4 GPUS and 1 PSU is wiring the 6 pins and satas of the 2 other GPU's? With satas i mean the sata risers.
I was wiring a riser that was plugged R9 series over it using SATA (almost one year without issue), but that was not safe. But I've no choice. I didn't have another secure connector (Molex / 6 pins) to wiring it. As you know, we have zero control to manage power used by GPU (PCIe bus or the other one that will be used first), each brand and series have different power management.
In your case, since you were using 1060, SATA was enough to wire a riser, but if you have enough Molex or 6 pins connector, will be better to use it.
Soon you will hear that SATA was enough for your setup. But remember, if you can doing with a safe way, why not? , Because your devices were your asset.
Then about wiring the cards (6 pins), as long as your 1st PSU can handle 4 cards plus Board (and everything on it), that's okay. If it not, changes current wiring scheme!