I have a passphrase and an SD backup as well. There is some Bitcoin held under just the seed, but most of it is behind the passphrase. The SD backup I keep myself hidden somewhere innocuous. The partial seed phrase would be kept in my fireproof safe which is what a thief would target first.

I am much more concerned about accidental loss than theft. First of all I trust these family members implicitly, so I'm not worried about them trying to steal or collude. They will know my passphrase without having to have it written down.

If the partial phrase was stolen it would likely be by a petty thief that doesn't have the knowledge or expertise to brute force a partial seed phrase on their own. Once I learned the partial was compromised I would move my stack to a new address immediately.

If I were ever targeted specifically for my Bitcoin I think I'd be fucked no matter how I do my setup. Most likely it would be a wrench attack, and if I was physically unable to give them what they want because of a multisig it wouldn't stop the torture anyway.

This is the best I've come up with and I feel pretty good about it. I already have the 24 word phrase (that Passport gave me btw), so I'm not switching now.