Airgapped devices are also good if you know what you are doing. You can also use airgapped device for seed generation. As long as you format the device and reinstall its OS with the Bluetooth and WiFi card removed, then you have nothing to be worried about.
I wouldn't trust entirely airgapped devices.
Even airgapped machines might be infected via BIOS/EIFE (and or hardware drivers) malicious payloads.
You can not get completely airgapped device as machine might be subjected to pre-shipment inspection by manufacture that includes the checking its connectivity to Internet.
I think you mean EFI, EFIE isn't a word.
Anyway, during the process of fiddling with OpenCore EFIs, I have learned a lot of information about how EFI works. In the /boot partition there is an EFI folder that contains all the files and stuff which are read into the computer before booting the OS. Since you can actually verify what is in your EFI and replace it with a non-infected file if you find you really need to, then it is trivial to do so as superuser or admin. I don't think BIOS has that kind of capability, and actually it may be
burned in to the motherboard in such a case and firmware update that is in many cases, non-existent.
Therefore I would prefer to use the newer EFI systems over BIOS to set up an airgapped system.