As this is a bronze rated PSU and not a modular one. I'll recommend not using any adapters to gain more connections for more GPUs. However, I'll recommend you to invest in a Gold rated PSU, Corsair RM850x is a personal favourite of mine. It can easily handle 8x GTX1060, and way durable to handle 24hr operation, so you won't regret investing in one.
I'll take a look into it. I wonder if this Bronze unit (
http://www.skytech.lt/m12ii750-evo-seasonic-m12ii750-evo-edition-750w-plus-bronze-retail-p-294241.html) is worth to get while saving 40EUR compared to Corsair? My wall draw will be max 550W.
Using SATA connectors for risers is a BAD IDEA, SATA connections are not rated for the 75 watts (nominal, sometimes HIGHER) that a common GPU pulls from the PCI-E bus.
Well I am running my GPU's not at full capacity, but downrated to get max MH per Wh of electricity and SATA wires are cold (with 3x GTX1060). On the other hand which connections are preferred to power risers?