Are you meaning use an email address that doesn't use your real name or an alias for your real name? Honestly it just depends on what you are using it for. If you are using the address for friends and family and things attached to your real identity I guess you could use your real name for both. If you are are paying from proton with fiat you will have to use your real name as well for the billing I believe. However if you have a more private use then yeah use an alias.

The main difference between Proton and Gmail is that with Proton your email is encrypted at rest. Gmail reads your email to show you ads. Unless you use PGP or Proton's secure message feature the email is sent just like any other email service.

Also, you are of course trusting Proton or whoever you use for email. Email is not a secure messaging system. It can be more or less secure and private but it is important to understand the limitations.

As far as Graphene, yes they recommend the phones manufactured by Google. This is because of the hardware's quality and open design allowing for modifying the bootloader. These phones are high quality and as far as we know they are not compromised. Google does their tracking in the OS and apps and they do a ton of it.

Hope that helps. Others can add to what I have here I'm sure.