Why are most peninsulas oriented north-south?
Starting from the bottom of your question I would not compare planets with plate tectonics with planets that don't have this process. During rifting of a tectonic plate a triple junction will be the most favourable way of faulting the crust. After that two arms of the rift are favoured and the third one becomes a failed rift (aulacogen). Because of this process linear features on a planet will be very emphasized.

The current geometry of mid ocean ridges and subduction zones does fall into a strong north-south pattern (Exceptions are Antarctica and the Aleutian trench). This might also be due to the fact that the plates form a system that in all its complexity still strives for lower stress and effective heat transport. In this case a parallel system of mid-ocean-ridges and subduction zones might be more favourable than a totally random alignment of those features.

The dynamics of the inner Earth are of course not independent of the plates and it is difficult to assign causality. Nonetheless you could again think of a complex system that seeks for efficiency (pragmatism if you will). With subduction plates being plate-shaped, circulation above and beneath them will probably be more stable in a cylindrical fashion. So the heat distribution on the upwelling side of the circulation should also create linear features. In any case we just happen to live in a time where the system went for a North-South oriented minimum.

Continuing this thought process we can also find an explanation why features in this tectonic-north-south part of the world are oriented in this way. Many north-south striking islands have north-south striking back-arc-basins that separate them from their main land masses. And peninsulas are sometimes the arms of failed rifts or the tapering of back-arc-basins. Outside of this prevalent orientation we see features like Nowaja Semlja with very different orientations.

But be cautious with this theory. Assigning each feature on Earth to a north-south and east-west orientation gives you a 50 % chance that a randomly aligned feature will confirm your theory. Even four directions still give you 25 % chance. So the more directions you consider the harder it is to prove the theory. I am not aware of anybody doing a global peninsula inventory, so it would be interesting to see this.