SLi Primary GPU selection

Hello,
I've got a question or two about SLi-ing 2 cards.
Can I use the second GPU as the primary by plugging the DVI cord into it (ie, does plugging the display cord into any card set it as primary), or does it have to be set within the nV software settings. I am using Afterburner, does Afterburner allow you to set it?
Ex:


Or can the second GPU in PCIE slot 2 even be set as the primary? My motherboard is a P8Z68-V/Gen3 - 2xGPU's will be running x8/x8.

And are there any restrictions between two different brands of 4xx Fermi cards and SLi or is GPU and Vram continuity all that needs to be matched?

Sorry if this was confusing. This is the first time I've ever stacked video cards together.