The way I see it, different people have a different approach to role-playing, someone will play making decisions based on what they would do in a given situation, someone will try to do it from Geralt's perspective, but then things vary on each individual interpretation of him. A person may choose to imagine and play Geralt as a gigolo monster slayer with the knack for eating insane amounts of chicken every day and that still wouldn't be the wrong way of playing it. I just don't think there is proper way of playing a game like this and within the boundaries CDPR offered we can all create and enjoy our own story with whatever role-playing approach we take.
Like I said, any way you choose you'll interpreting someone. Even your own image in the game, that's an essencial part of RPG.