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.
This is a hypothetical question. i want some expert opinion to confirm my bias that offline transaction on airgaped pc is more secure than a trezor.
If you are making that question, it is because you are not comfortable with the technology
They are both safe
as long you understand how to make an offline transaction safely.
As you don't look like a "tech guy", my suggestion is that you use a hardware wallet.
Hardware wallets are designed to be easy to use and safe. You won't make a mistake using a hardware wallet. You will be fine.