Earlier quoted context omitted.
Absolutely use a password manager, and a strong passphrase for the master password [1] Why would you say not? I'm not trying to be rude or anything. Let's have a discussion, and if I can convince you to do use one, I'd have made one more person safer. [1] I made this for a dead simple way to make passphrases: https://amingilani.github.io/password-maker/
Not OP but open for a chance. Last time I checked the popular password managers saved the passwords in one way or another. Which personally simply sounds like a bad idea to begin with. Even if in theorie they are safe. Even the slight chance that a single failure could lead to all my passwords getting in the wrong hands at once just is to scary.
1. Are all your passwords unique?
2. If I discovered some of your passwords, will the rest of your passwords stay secure?
3. Were all your passwords created using at least 32 bits of entropy?
4. Are your passwords stored only in encrypted form?
5. Do you perfectly remember every single password you’ve used when signing up?
6. Do you turn up positive for a password leak at this website?
If you answer "no" to any of these questions, you'll benefit from a password manager.
About storing passwords, I use LastPass and they use client-side encryption[1], which means even they don't have the decryption key to read my passwords. So, you'll be fine as long as you have a secure passphrase and 2FA :)
https://lastpass.com/support.php?cmd=showfaq&id=6926
[1]: Please skip to "Strategy No. 1: Proper Password Management" @ https://www.toptal.com/remote/best-security-practices-for-re...