Multiple GPUs or K2200 (4GB) vs K4000 (3GB)


I am rebuilding our graphics rendering server with a threadripper 1950x build. It will have 32GB of quad channel ram with a 1 TB 960 pro NVME SSD to start with for both system and video. I have a Quadro k2200 with 4GB of graphics ram from the old system and a Quadro K4000 with 3GB of graphics ram that was just donated. The video card is a decklink quad 2. We will be runing key/fill for graphics on channels 1/2, projector feed input on 2, clock and alert overlaid on ch3 output on channel 4, and channels 5-8 will be for streaming encoding and various disk consumers as computing power allows. Currently we are still running SD widescreen on most channels, but CH3 input and CH4 output will be 1080i.

Can CasparCG use two rendering cards at once like blender does, or would that just be a waste? If I have to choose one card, which would you recommend? Many benchmarks have the K2200 coming out ahead of the k4000. Thanks to threadripper's 64 PCIe lanes, number of lanes shouldn't be a problem. The old computer is a Phenom x4 965 socket AM3 machine with questionable motherboard stability, so that computer will most likely be retired. I plan on upgrading the GPU and adding more SSD's when we convert our main production chain to HD or 4K.

To summarize, will running both cards be beneficial, or should I just run the more capable one?
If so, which one is likely to be most capable for this application?