Blockstream Jade/Green Setup Questions

Throwaway account. Seeking clarification…

1. When setting up multiple accounts within the same wallet - what happens if you wipe your device/app and then reinstall the wallet - do the accounts come back? What if you load your seed onto a different hardware wallet (Ledger, Trezor, etc)?

2. Regarding Passphrase…Blockstream recommends setting up two; one to use as a decoy with a small amount of Bitcoin and the other as your main address. Is this any better than simply using the seed phrase as the decoy account, and the Passphrase as your main account? Seems easier than keeping track of two passphrase plus your seed phrase.

3. I tried making a new wallet after factory resetting my Jade. After generating a new 12 word seed, TWO devices popped up as discoverable in the app (I was only able to connect to the one I had in front of me), and the other one already had a custom name associated with it. What the heck was this? Could it have been picking up a Jade from a neighboring house, or could this freshly generated 12 word seed have already been active? I tried to connect to it but was unable to.

Thanks