spout should not cause any network traffic. It's about texture sharing on the same machine directly on the GPU. So even only little performance loss.

4k signals thru AJA hardware are not supported in Resolume. For 4k signals you're best bet is probably a Decklink 4k Extreme 12G should you need to stick with SDI. If you are going to output to LED walls you could also look at (framesynchronized, not tested with Resolume) Quadro GPUs. You will not h...