I use my iGPU when mining so I don't get screen lag or reduced hashrate.
If you also have a discrete GPU, my understanding is that you could use Mining Controller against that instance and mine on both!
I do use discrete graphics cards for mining. The display output source is set to the iGPU in the motherboard BIOS. I am unaware of CG/SGMiner of being to able mine with Intel iGPU or why I would even if it could.