So, about character customization.. did anyone look at youtube description?
Watch the E3 trailer for Cyberpunk 2077 — the role-playing game of the dark future from CD PROJEKT RED, creators of The Witcher 3: Wild Hunt. Cyberpunk 2077 is a narrative-driven, open world RPG set in the most vibrant and dangerous metropolis of the future — Night City. You play as V, a hired gun on the rise, who just got their first serious contract. In a world of cyberenhanced street warriors, tech-savvy netrunners and corporate life-hackers, today is your first step to becoming an urban legend. Cyberpunk 2077 is set in the same universe as Mike Pondsmith's classic pen & paper RPG system, Cyberpunk 2020.
It says you play as V, a hired gun who just got their first contract. Maybe this helps to answer if its a fixed protagonist? Were ito so, they would probably call V as Him, not their, which could suggest character creation.