Bip39 Standard. You'd probably then do a simple recovery that has a command much like the a single underneath. (This command works by using a sample wallet file bunlded with BTCRecover) No, there isn't any specialized Restrict on the length of one's passphrase. Even so, for that sake of memorability https://thefairlist.com/story8696945/bip39-passphrase-https-linktr-ee-bip39-the-2-minute-rule-for-bip39-word-list