If you ask about best secure way to file encryption and password manager here you will find the answer
SuProtection its open source project, help you secure file encryption and password manager
It provides an easy feature to encrypt files and passwords,
as no one can decrypt files or passwords and view them because
they are encrypted using a password and only you can see the files.
Screenshot
also you can check this video :
Protect your data and passwords with SuProtection