For lock removal, any region will work as long as your SIM supports it. Avoid "Carrier-branded" firmwares (like T-Mobile) as they have extra bloatware.
An FTF (Flash Tool File) is a type of file used by Sony's Flash Tool, a software application designed to flash firmware on Sony devices. An FTF file contains the necessary data to rewrite the firmware on a device, allowing users to upgrade, downgrade, or modify their device's operating system. Sony G3312 Lock Remove Ftf File