Lets say i want to transact a very important huge amount of btc transation of my life. Which one should i chose between Offline signing transaction via Electrum(gpgverified) or trezor bought from official site.
Using airgapped pc for sending transactions is fine if you are security expert and if you know what you are doing,
but if you are average crypto user without confirmed clean computer and linux operating system, than it is probably easier to use trezor hardware wallet with passphrase option.
Both devices are not connected to internet and there are pros and cons for both approaches, if you don't already have airgapped computer it would take time installing and setting everything up.
Ordering hardware wallet devices can also be problematic for privacy so I would suggest using PO boxes or alternative address and reading this
[GUIDE] How to buy a Hardware Wallet the right way.