- What's the safest way to store BIP39 seed words?
- What hardware wallet backup options exist?
- How can I share details on wallet maintenance with family?
Some specific answers to your questions.
I don't know that there is a great answer to this. Your options range from putting it on paper and in a safe deposit box in a bank, to storing it one word at a time in random places (like an escape room scenario). There are some very cool physical devices for storing seed words that are made if metal to be fire resistant. Basically you use a punch to mark the seed words in the metal.
Hardware wallet backups are similar. You just have a list of seed words that you need to protect. One nice thing about Hardware wallets is that you can restore a second or third wallet with the same seed phrase and store them in separate locations.
This depends on your family and estate management scenario. Do you trust your family? It can be a good idea for you to share the details of your wallet with a spouse or parent that can manager your funds if you are incapacitated. You can also have safe-deposit box ownership be transferrable to someone should you become incapacitated and inside have instructions for them on how to manage your funds (a will helps here).
Some more thoughts...
Wallet safety, as any other cyber security question, comes down to risk vs. effort. That is, how much is what you are trying to protect worth and how much effort and expense are you willing to put it to protect it? The billions of dollars in Bitcoin on the Tesla balance sheet is managed much differently that my grandpa's $100 of crypto.
This is of course up to the individual, but something like below is what I tell people.
- < $100 worth
Standard software wallet with seed phrase in a password manager shared with a family member is probably fine.
- In between is kind of a grey area.
- > $1000
This should definitely be on a hardware wallet if possible. Family members can share the PIN/passphrase (ex. in case of emergency who can access your funds?). The seed phrase (hardware wallet backup) should be stored off of a computer! You can store the seed in multiple places such as a home safe or bank safe deposit box if available (again your level of risk will help determine this). It's also probably a good idea to leave instructions for family.
- ~$1M I probably wouldn't want these seed words stored in my house...