It will depend on the details of your device, so it is hard to give advice without seeing the script.
However, one thing you can do is to make sure threading is enabled. It will allow you to re-gain some of the performance that is lost when you reduce the number of processes. Also, make sure you distribute the processes equally on the node, to ensure that you can utilize the available memory efficiently. How to do this in practice depends on the hardware and queuing system, and cannot be done from inside QuantumATK.