The idea is to have multiple cryptocurrency accounts, it doesn't cost anything; multiple accounts create a hierarchical structure of more or less important accounts; the same goes for wallets - two, three, four or more non-custodial wallets, from which so-called cold wallets are rarely used, hidden from the world, intended for storing assets and other so-called hot wallets - more frequently used, visible to the world, intended for managing smaller assets

A wallet is a program that runs on your computer or phone.
An account is information about funds existing on the network. The account itself also exists on the network, not on a computer or phone.
Whoever knows the secret of the account (private key) owns the funds stored in the account.

Higher-ranking wallets feed lower-ranking wallets. Which wallets hold the secrets of which accounts? It depends on needs and imagination.

For this, one smartphone or laptop is not enough. This implies having many devices. Laptops, mini-computers, etc.

Taken the matter seriously, a hardware wallet will not occupy a high position in the hierarchy of wallets and will not store the secrets of important accounts, neither a smartphone app wallet nor a browser plugin wallet.

Online custodial wallets located on remote servers on the internet are the lowest level in the hierarchy. They should not be used to store funds, but only for currency exchanging or small expenses.

The reliability of the whole concept requires the redundancy of selected, most important non-custodial wallets. It is about the conscious use of many separate computers and a well-thought-out strategy for storing them. The point is the security and absolute exclusivity of possesing and storing account secrets. Not on the Internet, but on own devices.

A BiTCoin owner who does not maintain at least one node/wallet of their own? This is an unaware owner.

ALTcoin resources if not placed in their own secure non-custodial cold wallets? These are volatile assets.

Your own ALTcoin node? This is a topic for those who know.