For an application that does strictly animation, then two CPUs should be sufficient. Green threads will not take advantage of multiple CPUs. If the application is a first person point of view application, and the environment is well known, Switch nodes may be used to implement simple occlusion culling. The children of the switch node that are not currently visible may be turned off. If the application has this kind of knowledge, this can be a very useful technique.
Most animation is accomplished by changing the transformations that effect an object.
If the animation is fairly simple and repeatable, the flip-book trick can be used to display the animation. Simply put all the animation frames under one switch node and use a SwitchValueInterpolator on the switch node. This increases memory consumption in favor of smooth animations. To create a shallow clone of the scene graph, use cloneTree without duplication the node components. They disable any state sorting optimizations that are possible.