“Panentheism” is actually defined in a number of ways–a case can be made that St. Thomas Aquinas and most traditional Christian theologians were panentheistic. Whether panentheism has to involve an “impersonal” God is questionable, as is the term “impersonal” itself, which, again, can mean a lot of things. Christians do not, after all, believe that God is a Person, since we believe he is three Persons
The thing to bear in mind with Hinduism is that it has followed a completely different trajectory and the “big questions” have been asked independently of the way they’ve been asked in our own cultural tradition. It looks as if maybe ancient Greco-Roman religions were heading toward something like Hinduism (at least the Neo-Platonists sound very much like Indian philosophers at times, though that may have been because of direct influence). In both cultures, how philosophers thought about God and how the “common people” did were very different, but in Hinduism as it developed the two were much more interrelated, I think. The chasm between philosophers and “hoi polloi” in the Greco-Roman world was perhaps one of the reasons Christianity “won.”
The big difference I see between Hinduism and the “Abrahamic” traditions is that it has no conception of idolatry. There are forms of worship that are “lower”–addressed to “impure” gods for purely material ends. But they aren’t seen as being bad in the way we see idolatry as bad. So the polytheism/monotheism distinction (which is fundamentally about worship) doesn’t make any sense in terms of Hinduism, I think.
I could go on, but that’s enough of my ranting for now
Edwin