The submission type field in your screen shot is the same field you would see in other types of Canvas assignments. If you start creating an assignment, you can choose online submission, external tool, paper, or no submission there. When you start creating a New Quiz, Canvas creates an assignment that will connect to the New Quiz (which is in a separate application) and sets the submission type as external tool with New Quizzes set as the tool. If you could edit those fields, it would mean you could change which LTI the assignment connects to or which kinds of submissions students will make to Canvas. But then it wouldn't be a New Quiz assignment.