I don't see password managers as a secured way because once your device is lost, you have lost access to your password managers also. Making multiple copies of your passwords on paper make your password more vulnerable.
If you can not memorize your password, then I'm sorry to say that it's not important to you. I backed up the idea of memorizing and make a copy to save in a vault. Apart from vault I'm yet to see a safest place to store security credentials.
That's why you need to separate your device and copied it to all your device to prevent from this kind problem, secondary phone is very important and I don't think everyone can't afford to bought two phones while most of cell phones are cheap.
If your password are very secure, full combination of capitalize, number, symbol etc it's almost impossible you will always remember your password. More importantly you shouldn't using one password for all platforms to make it more secure.
Bank vault isn't safe since they can read your password, it's better to make your own steel plate contain your password.
To @OP don't ever login your password to your friend phones, even you've logout, the keyboard could still remember your password.