Worst case for your Protonmail account is losing access to your email (which you can almost fully mitigate by using your own domain and having backups).
Worst case for your Google account is losing access to hundreds of Google services and anything you paid for, like apps or movies. And Gmail doesn't even allow you to use your own domain, other than by paying for G Suite which is clearly not targeted at individuals and doesn't work well if you try to use it as an individual.
If in the future Protonmail extends into other areas like Google does, and you start using these new services, it would absolutely have the same risks.
