1060s will be fine using both plugs on one cable. Just avoid using splitters, since you definitely shouldn't need them for that configuration. (Extenders may be desirable.)
Alternatively, you could use a 2x molex to 1x 6-pin PCIe adapter, and just have one PCIe cable from the PSU for the rest of the cards. The cables, as you said, have 2 connectors at each end, but those two connectors aren't spaced far enough on the cable to give you much flexibility with card placement. (You might be limited to about 4 inches between the two cards on the same PCIe power cable, if you go that route.)
A 750W EVGA PSU will probably do the trick for 4x 1060s, under the assumption that you're not doing anything wacky with your CPU/motherboard/drives/fans/etc. (Specify them if you're unsure what I mean.) However, do keep in mind that the BQ series of PSUs is about as low as you can get from EVGA right now. They're *probably* fine, but IIRC, the guts are manufactured by HEC, which isn't quite as reputable as manufacturers such as SuperFlower, Seasonic, FSP, etc.
Also note that a beefier PSU will give you more room for expansion, unless you'd be willing to purchase a second PSU in the future.
SATA risers are okay if you're careful,as leonix007 said, to avoid connecting too many risers to one line of SATA connectors from the PSU. SATA connectors are not rated to handle the same current as the other two, although you can usually push them a little past the official rating (not ideal). However, if you can get 6-pin or molex risers for similar prices, I'd just go ahead and use those. (Unless you're that concerned about needing adapters for your PSU connectors.)
PSU got a decent review from the Guru. But im in no way dead set on using it. I am running to many computer as it is so i was thinking of running these cards from my back up PC. It will be running the 4 cards, 1 SSD and 3 old 2 TB green drives i keep around for back ups. It has 2x 120mm fans and another on the CPU (an old e8400 at stock) cooler. 4 Sticks of DDR2 RAM. Nothing really crazy.. hehe. Too much?
