My new Hackintosh is almost finished, but I couldn't get a workflow as simple as yours: I have two HDMI cables in my monitor, one connected to the Titan and another connected to the IGFX. If I boot Windows with the IGFX and then switch to the Titan, I get an empty desktop where neither the mouse nor keyboard work. Only the IGFX desktop is functional if I boot with the IGFX. So, when booting Windows or Linux I enter first the BIOS and set the default graphics to "PCIe slot 1" and the IGFX as "auto". When booting OSX I enter THE BIOS again and set them to "IGFX" and "Enabled" respectively.
I wrote the Win+Linux vs OS X boot procedures in a paper and it looks like a checklist for takeoff
But at least it works