1Password was designed to be the only password manager in your browser, so utilizing another password manager (such as the browser’s built-in autofill) will definitely cause some conflict, which is why we recommend disabling it: https://support.1password.com/disable-browser-password-manager/
In case you do wish to keep using your browser’s built in autofill, you can go into the extension’s settings page and turn off the “Show autofill menu on field focus”, which will prevent 1Password from showing up automatically inside/under fields. :)
