As a director, I have to feel realism from actors, and they can't be plastic. The words for me are secondary, but the chemistry between the actors is most important. However, you have to go by the script because it's related to production, otherwise you will not finish your project. My background are acting, film production, directing, and I studied them for many years. Keep in mind that you need many other skills when you are starting any film project related to real life.