Nowadays, most people use password managers (hopefully). However, there are still some passwords that you need to memorize, like master password (for a password manager), phone lock, wifi password, etc.
Security wise, can passphrase reach the strength of a good password without getting so long that it defeats the purpose of even using it?
If you’re using one password for all those things, you’re doing it wrong. Even if the passphrases you pick are easy to remember and type, they should be distinct.
If it’s one “account” then it likely has only one password.
That’s SSO for you