I understand that it’s a very big and difficult topic however I was wondering whether or not all Mefarshim and Rabbanim hold of the opinion that people can come back as other people in another life or as animals. I even heard that big Reshaim can come back as things such as a rock. I was under the impression that a soul isn’t sent back rather elements of the soul are present in a completely new Neshama. What truth is there in this and are there any sources from the Torah to support such beliefs?
As you said it is a big topic or more than that - an esoteric one. I have not enough knowledge to share with you and I have read the same things you mentioned in different books. It is also true that the Gilgul concept is not fully agreed among all authentic Jewish authorities, though the Ar"i z"l has a whole chapter on the topic, and on these issues it is almost impossible to dispute the Ar"i, as who can say he is as great as the Ar"i was?