For an application that does strictly animation, then two CPU's should be sufficient. Green threads will not take advantage of multiple CPU's. 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 flipbook 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. OrderedGroup Nodes OrderedGroup and its subclasses are not as high performing as the unordered group nodes. They disable any state sorting optimizations that are possible.