Use a 12V relay module because it can connect directly to your source.
Use a logic level converter to bring your 3.3V logic from the ESP32-CAM to the 5V necessary for the relay. There is an audible click with some relays, you can avoid it with solid state relays if needed.
Use a buck converter to bring your 12V down to 5V to power the ESP32-CAM with enough current to prevent a brownout.
You don't need the Nano, save it for another project.