If you do not setup Multisig wallet/s well you may end up paying more fees without enhancing the security
If you use Taproot then you can make multi-sig transactions without any increase in fees.
This is an excellent solution for Bitcoin, but you will not have multiple options if you intend to store some altcoins
For the vast majority of altcoins, you are exponentially more likely to lose your money due to them being useless, scams, rugpulls, Ponzis, completely centralized, and so on. If you are concerned enough with the safety of your money to be thinking about hardware wallets or cold storage, you should be concerned enough to swap all your shitcoins back to bitcoin.
No reason to choose one or the other, both can be used in unison for a very secure and private set up. One signer wallet on an online machine with the other on an air-gapped machine can be a practical set up. It's not so much different than having an encrypted watch only wallet on the online machine, but chain analysis freaks out when it sees a 2 of 2 multisig transaction, especially if there are multiple inputs. And I like fucking with chain analysis.
The only caveat with combining multi-sig and an airgapped machine is that you can completely negate the safety that airgapping brings. If, for example, I set up a 2-of-3 between phone, daily computer, and airgapped computer, the airgapped computer adds absolutely nothing since the compromise of two hot wallets (phone and daily computer) is sufficient to steal my coins.
You need to ensure you cannot reach your threshold number of keys without at least one airgapped wallet. Your 2-of-2 example works. Another example with some redundancy would be a 2-of-3 between daily computer, airgapped computer, and the third seed phrase only on paper as an emergency back up.
Can someone please point me in the direction of a good air gapped wallet strategy?
Here are the basics:
Two devices. Both formatted, clean install of good Linux distro of choice, full disk encryption. All software verified prior to installation. Both devices used for nothing else and kept physically and digitally secured.
Device 1, internet connected:
Your own node running over Tor.
Your own Electrum server of choice.
Your watch only Electrum wallet connecting exclusively to your own server.
Device 2, permanently airgapped at a hardware level:
Your Electrum wallet containing seed phrase/private keys.