Then, if you've got a serious amount of Bitcoin, seeking a air gapped, completely offline solution would be beneficial. Something like a ColdCard, could do the trick. Although, pretty much any open source Bitcoin wallet is good enough for storing offline, as long as its stored securely. Obviously, hardware wallets allow users who might not understand the security risks, secure their Bitcoin to at least acceptable levels, right off the bat. ColdCard is a little more complex, and could potentially introduce errors if someone isn't entirely familiar with the process.