iCloud iCloud Keychain questions - Passkey related

[iphonefreak450]

I just setup a passkey for my Google account and for the rest of my accounts and works fine just using my iPhone.

However, in case I have to reset my iPhone to its default factory settings using the Erase all Content and Settings, then which option should I choose from if I DO NOT want to lose access to my Passkeys?

Should I choose KEEP MY INFORMATION or DON'T KEEP MY INFORMATION?
I assume that if I select Don't Keep my Information, then the passkeys will not be saved to locally to my device.
If that is the case, then how will I sign in to my accounts with the passkeys option?
Will the passkeys be re-synced again after turning ON iCloud Keychain again when the iPhone is restored after the factory reset?

So basically, how do the Passkeys get restored after performing the Erase All Content and Settings from my iPhone.

If you turn off iCloud Keychain​

• When you turn off iCloud Keychain, password, passkey, and credit card information is stored locally on your device.
• When you sign out of iCloud on your device while iCloud Keychain is turned on, you're asked to keep or delete your Keychain information.
  
  • If you choose to keep the information, your passwords and passkeys are stored locally on your device, but aren't deleted or updated when you make changes on other devices.
  • If you don't keep the information, your passwords and passkeys aren't available on your device. An encrypted copy of your Keychain data is kept on iCloud servers. If you turn iCloud Keychain back on, your passwords and passkeys will sync to your device again.

 

[Mike Boreham]

I think you are confusing “Erase all Content and settings“ with signing out of iCloud.

You are only asked if you want to keep a local copy when you sign out of iCloud.

Erase all content and settings deletes everything locally, returns phone to factory state. There is no option to keep anything.

Both of them leave everything in iCloud, so when you sign in again either on this phone or a new phone the Keychain data will sync down.

 

[iphonefreak450]

Many thanks for this information. Understand now.