Re: Gmail?
Protonmail is only encrypted end to end if you compose your email from their web client, and send your email to another Protonmail user (of which their aren't many in my address book). It doesn't however whore all of your data to advertisers like other services. I do have an account with them BTW, I just don't use it that much yet.
I'm with GMX for my primary mail account. I can't say it's been a bad experience and it seems quite reliable, although I may switch to a paid service like Startmail or such like fairly soon.