you can run 3 x 1070, but this depends on your motherboard.
some motherboards has the third pcie slot tied with the m.2 drive,
so you'll have to check your motherboard's manual.
yes, 6 wu's , 2 wu's per card you'll have to update your app_config.
usually for 2 wu's it would be 1 CPU + .5 GPU , so you need 6 CPU + 3 GPU.
the rest of the CPU's can do WCG, this is what i'm doing now, CollatzConjecture 2 wu's per card, set @ 1 CPU + 0.5GPU
and the rest of the CPU's on SAT@Home and GIMPS.
these card should be able to run on linux see -> http://www.nvidia.com/download/drive...x/105343/en-us
should work on a 2P system, here's mine...