This is safe, flashing and unlocking is safe. But tuning settings such as voltages and current in secret menu might harm. so only tune after research and understand the outcome.
During flashing, do not interrupt! If any error, simply start the process again. Just dont reboot yet until success.
RMA still covered thanks to asus. just in case setting goes wrong such as too much RAM OC, fully disassemble, remove battery connector, and bios battery connector for few seconds.
after bios reset every settings will back to failsafe state.