Beginners: paper cold wallet
Intermediate: USB stick with TailsOS and Electrum, Sparrow or Coinomi
Expert: commercial cold wallet.
The last two are actually reversed.
Using a commercial hardware wallet is at intermediate level for its ease of use,
and it may not even be "
Air-Gap" depending on the hardware device's source code availability.
On the other hand, USB stick with Tails require expertise to properly utilize a wallet's cold-storage feature
but the end result is as safe (
if not better) as the most reputable hardware wallet out there.