DeckLink 4K Pro playback and render speeds?

Will DeckLink 4K Pro play back 4.6k raw mini footage in real time in Resolve? How will it affect render speeds? Will upgrading to a gtx 1080 video card(from a much older geforce) have a much greater influence on performance(total nodes, render speed), than this hardware rendering card?

Decklink cards are not for rendering, only for capture/playback. For colorists they are used to send video directly to a (hopefully calibrated) display, bypassing any color management the OS is doing with the graphics card.