IC 4.3 and PayPal IPN?

[PoC2]

We've moved from IPS 3.4 to IC 4.3 and it's great but I have a query about PayPal and Commerce that I hope someone may be able to answer, namely:

We had/have subscriptions running under v. 3.4 and they used the PayPal IPN code/URL to work at PayPal's site. Is this still needed with IC 4.3 Commerce and "Billing Agreements"? All's fine for new subs under 4.3 so far, but I'm thinking of the legacy subscriptions. Also, is the PayPal IPN URL still need at the PayPal site for product purchases?

So far I've been unable to find a post/guide telling me the answer. Any info. much appreciated!