fastboot option is the safest and easiest method! To brick a device, u either need to have a loss of power and disconnection from your transfer cable during the flashing process. Even if that happen, there is always boot recovery from stock.
I suggest you to flash MIUI EU ROM to show xiaomi that you are unhappy with their OS and updates! while you wait for the unlock duration and the pain you will endure by Mi when logging in to Mi Account for verification failures, then you will be begging to unlock your bootloader!
I flashed mine for the exact reason and it fixed this 2 issue that my official ROM never fixed:
1.Option to turned off AOD self off while laying phone in dark room.
2.Turning off Bluetooth from top down menu will turn off forever and not 24 hours.
3. And many tiny cues, tweaks that come with MIUI EU! E.g Miui EU tweaks aren't perfect in a warm environment, but it is noticeably better in every aspect if you really understood your phone!
