Bootloader unlock problems?

Hello,

I bought a 64gb version throw gearbest and they installed a vendors version 7.3.14.0.0 not oficial rom. With defeats the purpose of the bootloader being locked.

I want to install the original miui 8 china or miui 8 from xiaomi.eu.
If I unlock my bootloader by submitting the request to xiaomi what I lose? What are the disavantages?
Does the fingerprint reader works on a bootloader unlocked phone with official miui 8 china?
Does it work with xiaomi.eu rom?

What are the features that cease to work with an unlocked bootloader with these two roms?

If I install xiaomi.eu rom without unlock the bootloader using Doom Slayer method I must not update by OTA or I will brick it, right?
And oficial miui 8 can I update by OTA?

Sorry for these questions but is my first xiaomi with locked bootloader and don't want to screw up by not knowing the consequences of each method?

Thanks in advance

from xda-developers http://ift.tt/2dpfFJA
via IFTTT