Links to Storage Methods
This page reviews published methods for backing up and storing bitcoin wallets.
Cold Storage Methods
The glacier protocol is a cold storage scheme. It teaches how to use multiple computers made by different manufacturers which help resist attacks like malicius firmware. The multiple computers are given the same entropy and the user checks that they result in the same bitcoin addresses and private keys. Users are advised to avoid sidechannels like audio, power, magnetic and radio.
The tutorial teaches users to deal with raw private keys and write them down on paper. deterministic wallets are not used, nor are full nodes. Users are instructed to look up their balances on a blockchain explorer website which damages the user's privacy and makes them trust the website for verifying the rules of bitcoin.
Electrum's cold storage guide
The wallet features seed phrases, deterministic wallets, offline signing. Unsigned transactions can be transferred with QR codes and saving to a file (which can be put on a USB flash drive or any other transfer method). The wallet can be backed by a full node if the user connects to their own server, but this is optional and does not happen by default.
The tutorial does not aim to discuss anything about creating a secure offline computer.
Rusty Russell's "Remarkably Unreliable Guide To Bitcoin Storage"
The tutorial teaches how to use a laptop as the secure offline computer. It uses ubuntu OS, and Bitcoin Core as the bitcoin wallet. The private key material is stored in raw private key format, not seed phrases (which bitcoin core doesn't support) and so the guide does not benefit from deterministic wallets. QR codes are used to transfer transactions between the offline and online computers. As the tutorial uses Bitcoin Core it enjoys the benefits of a full node wallet.
However, it recommends naively splitting keys (without using a secure key-splitting algorithm like Shamir's secret sharing algorithm), and so is insecure and certainly not well vetted.
Alexandr Nellson's Scheme
This method is relatively basic, glossing over important steps like how to properly airgap a machine, how to create and handle a strong passphrase, and how to back up your seed. It uses usb drives to boot the machine and transfer transaction information, which is a significant attack vector. It also isn't open source and is definitely not well vetted.
Other Storage Methods
Bitgoldwallet's Storage Methods
This site has a number of different storage methods of both the hot and cold variety. The methods are detailed and complex, and somewhat hard to read. It seems to have some odd recommendations, like using password protected PDF files and Zorin OS. More review required.