Bip39 Standard. At first it is best to store it Individually out of your seed. Getting your seed plus your passphrase in exactly the same location defeats the objective of using a passphrase in the first place. No, there is no technical limit towards the length of your respective passphrase. https://bookmarknap.com/story9313562/ian-coleman-bip39-https-linktr-ee-bip39-how-much-you-need-to-expect-you-ll-pay-for-a-good-bip39-generator