Oh yes! The load balance ratio is a big factor in structural model as to how useful adding cores will be.
To figure out if the model fits in RAM when solving a Static Structural model, make sure to set the Solver to Direct. Then when the solution is complete, search in the Solution Output for the term incore and out-of-core. The text there will tell you if the solution was run incore (entirely in RAM) or out-of-core.
If you are going to solve the same basic model many times, it is worth doing some benchmarking and see what the elapsed time is as you change the number of cores. Do 4, 8, 16 and 32 cores to get four points on a graph.
Infiniband has many versions in its history, but yes, that is better than gigabit Ethernet.