-snip-
BTW, is there any difference between "Electrum extended word" and a passphrase?
Basically: Those are the same when it comes to use-case. It changes the derived binary seed from the mnemonic.
Technically: There's one difference under the hood, Electrum's salt is: "
electrum"+ the user's seed phrase extension.
While BIP39 is: "
mnemonic"+ the user's passphrase.