Souk Oulad Mimoun is a practical city market rather than a tourist bazaar, and that is its appeal. Stalls sell produce, household goods, clothes, phone accessories, and the everyday odds and ends that move through a border economy.
It is worth a wander if you want to see Nador at work. Bargaining is normal for some goods, but this is not Marrakesh: keep it low-key, watch your bag in the denser lanes, and stop for grilled fish or a simple sandwich nearby.