Gameplay wise, you can be a solo, techie or netrunner, or anything between those. From the narrative point of view, V is a somewhat pre-defined character, (from the official description) a hired gun on the rise who becomes an urban legend by the end. You can choose a few bits of the protagonist's backstory, which will impact some dialogues and quests later in the game, although I would expect this to make relatively minor differences, perhaps it will be comparable to the save import feature in the Witcher series.