But you know.. there might be an exploit in the QR code scanner. So effectively, you are never 100% secure.
However, using a dedicated computer just for storing the private keys is definitely one of the most secure options.
I think the main reason for people to avoid hardware wallets are the physical attacks.
However those attacks can't be mitigated by an airgapped computer, unless you format it after creating the paper wallet.
But you could also do it in a ledger, just reset it always after use. (Pretty annoying and I don't think that's useful)