I have no experience in the use of memory. It will be necessary for the stored data to be editable while the controller is running and for it to be retained if the power supply fails. I don't know what type the memory should be, and I only have the faintest knowledge of using EEPROM.
I would prefer to use a Nano.
Thanks groundFungus - I was not quite aware that a Nano would have its own EEPROM. I'm off in that direction now!