Unfortunately I can't say anything about OC via BIOS flashing.
My Vega FE doesn't make any noise, except a little gurgle from the water cooling.
But now I got the driver 18.Q2.1 installed so that the Driver Switchmode/ Driver Options and Wattman work again.
First I uninstalled everything with the uninstaller (C:/AMD/<driver folder>/bin/Uninstaller.exe)
Then I reinstalled the driver 18.Q2.1.
Between by the installer asks, I want to execute the "Custom Install", this must be selected absolutely.
Then the installer asks if you want to install multiple drivers, which must be answered in the YES.
After the installation you can use the driver option to install the gaming driver and then use Wattman again.
A install guide from AMD.... https://www2.ati.com/relnotes/driver-options-user-guide.pdf