Except for the heirs?
I think to protect the private key is better to use a hardware wallet. Hardware wallets are also more resistant to viruses, malware, etc.
I think for heirs a good option would be not to give them the private keys, but to tell them how to find.
Or maybe you could even split. 12 words to one, and 12 words to another. Or a passphrase with one, and the seed with another.
About hardware wallets... I can't understand how does anyone still hold more than 500 usd in any wallet that is not a hardware wallet.