That is an interesting thing to look into. So much of our life is symmetrical. bi-symmetrical. And that seems to be because of our dualistic universe. So, a bi-symmetrical alien is probably the norm. And upright walking, so they can use their hands is probably also quite normal.

Anyway, that is a theory based a lot on our world norms. We really do not know what the physics are out there.

However, i am sure the aliens will come and visit, and we will then know.