If you have the tag of an xform.
Are there any methods or classes to help determine the the part occurence and the linked feature that is tied to that part occurence that go along with the corresponding xform?
You can get the xform object from its tag; you can then use the .IsOccurrence property and get the .OwningComponent and/or .OwningPart.
In the NXOpen API reference, take a look at the UF_SO* functions. These are the functions pertaining to smart objects. You can find the status, parents, features, etc using these functions.