The Gigabyte G1 Gaming SOC is their top of the line card, bar none. Versus the regular, "vanilla" Gigabyte GTX 980 Ti, the difference is considerable.
http://www.guru3d.com/articles-pages/gigabyte-geforce-gtx-980-ti-g1-gaming-soc-review,1.html
The reference card is the same as any reference GTX 980 Ti made by any manufacturer. You will never overclock a reference card to match the speed potential of the G1. The reason being that the G1 uses a very effective custom cooler and all custom, upgraded components that will allow for higher Turbo Boost clocks, much higher than the potential of the reference blower type cooler on the regular card. According to Guru3d: "The PCB board design is custom from Gigabyte build upon their Ultra Durable standard with a 2oz copper PCB and the usual gear like solid capacitors, Ferrite Core chokes, DrMOS MOSfets." The regular model does not have a backplate, in answer to your question.