Can became brick, not, do it brick. See the thread of the xiaomi.eu 6.12.8 the first rom on nougat for Mi5. a lot of people made hardbrick for their devices because they wipe system.
So, never, never, never manual wipe system partition.
Manual wipe system can become to brick the device.
Update/install rom have an install script that make the necessary modifications to the system partition.
There is not root in xiaomi.eu roms. If you want root you must install supersu.
There is no way to install xiaomi.eu roms without TWRP.
The vendors usually install custom rom throw engine-wire or unlock bootloader.