Grape works without an account. You sign in for the things that need a server: the Pro subscription, Grape AI and sync.
Signing in
Sign in with Apple or Google, from the Grape Pro tab in Settings on either platform. There is no separate password to manage. On desktop the browser handles the sign in and hands you back to the app.
What signing in changes
With a Pro subscription, sync starts keeping your devices in step and Grape AI becomes available. The sample notes that shipped with the app are cleaned up on the first sync if you never touched them.
Signing out
Sign out from the same tab. Grape asks what to do with the notes on this device: keep them, or remove everything local. Keep is the answer on your own computer, remove is the answer on one that is not.
Account versus app
Deleting the app or signing out never deletes your cloud data, and deleting your account never deletes the notes on your device. The two live separate lives on purpose.