The use of a Central manager is not required to accelerate traffic. However, without, you will not have access statistics reporting, CM software updates, GUI configuration and more.
All AA will have a default policy, but will need to use CLI to implement any advanced features. Highly recommended to utilize a CM in optimization environment as number of site deployments grow. Without CM each branch / core node needs to be administered individually as opposed to centrally using group policies.
Taking the cost into effect of admin for each device vs. ~6k for a manager kind of pays for itself.
The WAVE274 allows for up to 1000 managed devices.