One toggle does not back up everything. A complete Android backup is three pieces: system backup, photo backup and app-specific backups (mainly WhatsApp).
- 1System: Settings → Google → Backup → turn on 'Backup by Google One' (apps, SMS, call history, settings).
- 2Photos and videos: Google Photos → profile → 'Turn on backup'. Choose quality vs. original.
- 3WhatsApp: Settings → Chats → Chat backup → back up to Google Drive.
- 4Files: copy Downloads and Documents folders to Google Drive or a computer.
- 5Verify: check backup dates in Settings → Google → Backup before resets or phone swaps.
Tip: Free Google storage is 15 GB shared across Gmail, Drive and Photos. Back up over Wi-Fi and charge overnight, backups run automatically under those conditions.