Everything reachable from the gear icon in the top-right toolbar.
Email + password is the default. You can also sign in with a magic link (passwordless) from the landing page.
Settings → Account → "Change password." You'll be asked for the current password, then a new one (8 characters minimum).
If you've forgotten the current password, sign out, click "Forgot password" on the landing page, and follow the email reset link.
Settings → Account:
Settings → Account → Time zone. Drives "today" / weekday / midnight math everywhere. Defaults to your browser's resolved time zone.
Settings → Account → Export.
Settings → Account → "Delete my account…" schedules a soft-delete that hard-deletes 30 days later. You can cancel anytime within the window by signing back in.
Settings → Notifications:
Settings → Account → Sign out. Clears the local cache; your cloud data is untouched and re-pulls on next sign-in.