Using Dual monitors with Dual gfx

I have an upgraded gpu in my pcie slot which I currently have both monitors plugged into. I was wondering if I could plug my backup second monitor into my onboard Intel HD graphics and possibly gain a bit more gpu power or system improvement by doing it this way. I actually am not sure that my i5 processor isn’t also a gpu. I’ve heard that some i5’s and i7’s are dual processor gpu’s. Is that correct? I have an i5 650.