As in many parts of Europe, manual transmission cars are much more common and much less expensive to rent than automatic transmission cars.

I don't want to unnecessarily alarm you, but if I were relatively inexperienced driving a manual transmission car, I'd be a little nervous driving into the Atlas Mountains. If you are driving uphill and have to stop the car, you take it out of gear. Putting it back into gear is a somewhat precise moved--learned with time--that involves simultaneously releasing the clutch, letting up on the brake and giving the car gas. (Some drivers will use the handbrake to assist in the process, which otherwise involves your two feet and three pedals.) Done incorrectly, the car either stalls or starts to roll backward. Put it this way: It's been 25 years since the first time I had to put a car into first gear, from a complete stop, while going uphill and I still remember it--and remember how stressful it was.

Are you planning to fly into Marrakech, rent the car there and then drop it in Tangier/Tangier Med?

Honestly, assuming the train schedules are completely off kilter because of Ramadan, I'd suggest forgetting the rental car and sticking to trains.