You can power risers off Sata power. It's important to never use more than two connections per strand MAX. Since EVGA G2 PSU's have four connectors per strand, I would use a Sata splitter cable to distribute the load over two connectors and power up to two risers from each strand. You can also do the same with 4-pin molex connectors. MAX two connections per strand.
https://www.amazon.com/Cable-Matters-2-Pack-2xSATA-Power/dp/B01DV1Z5S6https://www.amazon.com/Cable-Matters-2-Pack-Molex-Power/dp/B01DV1Z22KI use version 6 6-PIN PCI-E risers powered by a dual PSU setup that has all the risers and motherboard powered by the same PSU and the larger PSU only powers the VGA power inputs on the cards. Each riser uses between 45-50 W.