Its 3-of-3 multisig with different passphrases, you can't really bruteforce that even if they were somewhat weak.

No secure locations needed, be smart... You should only "store" passphrases in your own head. Make them complex yet easy to remember.

You could even use a lengthy quote from a movie or book as a passphrase, so even if you forget parts of it, you can always look it up online.