To what extent is Macbeth the architect of his own fate?

Well I'm not sure I understand what you mean but the witches, Lady Macbeth, and Macbeth himself all contributed to his fate in that the witches supplied the "nouns", or his future titles, and Lady Macbeth supplied the "verbs", as in she urged him to commit the murders in order to attain those titles. Macbeth did the rest.