I use mailbox.org with my own domains. And I encrypt my inbox using a PGP key I manage myself.
My setup is pretty much the same what Proton gives out of the box, I just manage my own keys rather than replying on the company.
Yes, my provider can see my unencrypted mails before my key encrypts it, but I trust them enough and I don’t pass sensitive information using emails.
Not Chinese or Japanese scripts, but I do use other non-latin scripts.
And no, we don’t use a larger font size.