PayPal Commerce Platform, IPN URL?

OC: 3.0.3.3, PCP: 1.1.5

Two questions in one. Is the PayPal IPN URL required for the PayPal account configuration?

If so, should the IPN URL be in, "Notifications" -> IPN URL or "Website Payments" -> IPN URL?

And what should be the format of the IPN URL?
e.g.
index.php?route=payment/pp_standard/callback
index.php?route=extension/payment/pp_standard/callback, or something else?

Thanks for any advice.

Just to help others and thanks to Dreamvention:

IPN listener URL:
index.php?route=extension/payment/paypal/webhook