Passwords and social sign-in
You can sign in with an email password, or with Google or Apple. If you started with Google or Apple, you can add an email password later from Settings → Account — choose Create a password. Both then work for the same account.
If you signed up with Google or Apple and have never set a password, there's nothing to reset — use Create a password instead of the reset link.
Notifications
You'll be notified when an event you care about goes live. Turn this off under Settings → Notifications.
Devices
Signing in on a new phone or tablet registers it for notifications. Your libraries and reader settings are per-device, so a fresh install starts from the defaults.