I turned off ambient display and battery life is much better. I think ambient display is too bright and drain a lot of battery.
The real reason is that aod keeps the device from going into deepsleep which is a state the device normally enters when...
i just need to unlock bootloader?
Yes, that's required,
and TWRP of course
Could i install it without root?
You could install any Rom without root
Might be pretty bugless, because they were built with the amazing sources by cosmin.
I would like to say that the most reliable ROM is actually the Official one although it's a bit outdated, but a very big new update is coming soon (with Android Q and MIUI 11)
In term of Custom ones I would say the Revolution OS one is pretty good...