Hello.
I don't have a "Master" but a X670 Aorus Elite AX.
I have experimented with newer bios files and saw a slight decrease in performance, the board came with F9 bios, I tried F22b and F21. Wasn't impressed, so I rolled back to F9 and have been happy since.
I use the bios flashing option in the bios screen itself, personally, I don't trust GCC much.
I download the wanted bios file and unzip it to a USB flash drive, reboot, use the bios built in flash utility and you choose the bios file you want from the flash drive, it will then verify the integrity of the file, ask you if you want to proceed, it'll reboot and do another verify, then it will flash the new (old) bios to the board and then reboot.
Be patient during the reboot process, this can seem like the system has hung but give it a few minutes and the system will come to life once again with the newly flashed bios.
Once this is done, I normally go into the bios and choose "Load optimal settings" and save and restart. Then I go back into the bios again and set the things I need to set like EXPO, disabling onboard graphics, etc.
In the week I've had this new board, I must have changed bios'es 5 to 6 times (gigabyte support asked to for proof that F21 was slower than F9).
I use my system for VR only (Racing and Flight Sims) and every little bit of performance is needed in high res VR.
Some people are very worried about changing bios, now days it's pretty safe, only time it may be a problem is if the process is interrupted like a power outage. But then again, most boards these days have a flashback button on them (dual bios) so the board should be able to be recovered.
Take care
Regards: Jack