I think this can get even more complicated, based on an observation of real-world plate. Many of the plates have highly irregular shapes, and those with plate-peninsulas seem to have different parts of the plates moving in somewhat different directions relative to a neighboring plates. I assume this is do to the interaction of the forces from the main part of the continent's rotational velocity (which I believe is influenced by subterranean magma currents) and the friction and pressure caused by collision with neighboring plates. In some of these scenarios, it looks like a larger plate may be torn assunder by another plate smashing through it.