From what I read and understood from Proton’s docs is that their solution is actually less privacy preserving than a regular Bitcoin wallet. As your BTC addresses are associated with your Proton email one only needs to send you BTC, then one has the email connection to the BTC address though that transaction. So as long as they don’t have default coinjoins, it’s worse. But ppl will believe it’s more private because of their other products.

Also I saw no RBF or coin control.