Port Speeds on 200G FortiGate

I have a new 200g replacing a 100f. Due to the number of ports I need, I need to use the 5g ports on the 200G. Can these 5g ports operate at 1g speed? I cannot test it at the moment, I can set the speed to 1000full or auto in the CLI config but I do not want to run into any surprises during the cutover