That's fine. It completely depends on your threat model and your preferences. To this date I haven't heard anything negative about PIA except their owners, so it's fair to trust them. I just want to point out that you can have both with other providers.
Generating a random account number is a unique and great feature of Mullvad.
But other providers allow for the same privacy. E.g. AirVPN does not require a valid email address. Any random string works for all required fields (email, username, password). Payment via Monero is available too.
Njalla does require a valid email address (it sends a confirmation mail), but any tempmail provider works (which you could access through Tor). They also accept Monero.