How is the drive from Fes to Essaouira if I were to rent a car? I know the drives can be stressful in the High Atlas if you're not used to it, but how about along the coast? Is this a cheaper & faster option than 1) taking a train to Marrakech and then a bus to Essa or 2) train to Casablanca then a grand taxi to Essa?
Additionally, do you think 4 full days in Fes is sufficient? One of theses days will be spent visiting Meknes to see Volubilis & Moulay Idriss.