I like Proton. There’s less privacy when your recipient is non-Proton such as Gmail or Yahoo, so in those situations just be careful what you write. But when sending to another Proton user, it uses public key cryptography, so an email can only be decrypted and read by someone holding the private key that matches the recipients public key.
Proton recently introduced sheets. I concur with those here. Eventually I plan on migrating all my important email and abandoning my old gmail account.
There’s a huge attack surface based on the amount of fishing scams I get now.