I find it weird that they don't mention virtu mvp anywhere in the article but this is what you use to use both igpu and discrete "together." There are plenty of reviews on it from more reputable sites but it doesn't work how you think it does. It doesn't increase performance, in most cases you will see a decrease. The igpu is tasked to intercepting and removing extra draw calls. So it really only works when you are above your monitors refresh rate. It is artificially raising the fps because it is not tasking the gpu to render the frames it removes but the fps counter still counts them.
It would be nice to have the igpu actually offload graphics rendering but this is currently not how it works.