Bip39 Checksum. Before everything you should retail outlet it Independently from your seed. Owning your seed and your passphrase in the identical location defeats the objective of having a passphrase in the first place. What constitutes a "very good wallet" is one which has crystal clear, simple to access documentation https://exactlybookmarks.com/story19285707/bip39-passphrase-https-linktr-ee-bip39-what-does-ian-coleman-bip39-mean