Where to connect 2nd display when you have dedicated AND iGPU?

So, my new system has ASRock Z77 Extreme6 board with Radeon 7850 dedicated GPU and Ivy Bridge i5-3570K. I initially thought that you have to use EITHER dedicated OR iGPU for everything, and that you couldn't use them simultaneously (like having your main monitor connected to Radeon and secondary on iGPU). I also thought that Virtu MVP is the thing that bridges the two and allows for greater flexibility with things like these. I had Virtu MVP installed originally but uninstalled it later, as I didn't think I'd need it.

Well, today, I messed with getting my HDTV connected to my computer as a secondary display, and sure enough it worked when they were both on my Radeon. But then I connected the HDTV to the iGPU, while leaving my main monitor connected to the dedicated Radeon GPU, and it still seems to have worked. The desktop is extended, I can drag windows from one to the other, set separate resolutions, etc. In Catalyst CC, I can control the Radeon settings, while the Intel Control Panel allows me to mess with the iGPU.

Does this seem normal? And if so... Should I run the HDTV off of the iGPU or not? If I play games or something, does that mean that the dedicated GPU will have a little less to struggle because it won't have to maintain that secondary display (because it's handled by iGPU), or what?

Some light shedding would be great here. Thanks!