That configuration won't work (only one of those GPUs can be used) but you don't need to use the onboard since that video card supports multiple monitors. COnnect both monitors to different ouputs on the card.
Not sure on that, but I do know that something (which I suspect is the iGPU) is taking its own bite from my RAM.
How could I test if the iGPU is at work? I assume dragging Furmark onto the iGPU screen isnt going to cut it