Triple monitor gaming, 4k Central and 1080p peripherals? Rendering?

[Brimstone_1]

I have a single 27" 1080p monitor and want to 4k game once the new Pascal GPU's become widely available. Which means I will likely be getting a 27" 4k monitor. And then I'll be one monitor short of a three screen setup.

If I purchased another 27" 1080p monitor, would I be able to game with the central monitor rendering in 4k and the peripherals rendering in 1080p? Or, would I have to render all three in 4k and simply have the peripherals downscale to 1080p?

I don't see a major benefit to having 4k peripheral screens for the added cost and I want to maximize performance by not having to render the peripherals in full 4k if I don't have to.

 

[Brimstone_1]

I know there are similar titled threads on the forums, but that thread isn't asking the same question as I am. That thread is asking only if their GPU will support three monitors, one of which happens to be a 4k monitor, mine is specific to the rendering aspect of the setup.

Can you render the peripheral monitors in 1080p and the central one in 4k? or, do you have to downscale the peripherals from 4k?