Hello,
Quiz categories are used to split by category (for example by different topic and etc.).
Question categories are used inside a quiz to separate quiz questions by topics (or levels of difficulty and etc.). It is also possible to select necessary number of questions from each question category. Questions can be created in quizzes directly without question bank.
Question bank is used if you want to use the same questions in different quizzes and edit them only in one place. Question bank is not required if each quiz uses own questions.
Bank categories are used inside bank questions to split questions inside question bank. It helps to separate them by topics, possible to configure a quiz to select necessary number of questions from question bank from selected category and etc.
About score for questions. Check "Score" parameter in question settings. If it is set to 0, users will earn 0 points for correct and incorrect answers (if "Penalty" parameter is also set to 0). For example set "Score" parameter to 1.
Regards,
ARI Soft