I’d go simple. Skip the deep fryer. Skip the foil. Cook them start to finish on the grill. Fried fish and fried potatoes gets a bit heavy for me and these taste better than any fries I’ve ever had.
Use the large white russet baking potatoes. Wash well. I don’t peel them, but you can. Cut each potato into 8-10 pieces. Try to keep the pieces less than an inch thick.
For every 2 pounds of potatoes… mix 1/4 cup of light oil, 2 T shredded Parmesan cheese, 1/2 t pepper and 1/2 t garlic salt in a bowl. Toss the potatoes in this mixture until coated. Grill over low/medium heat for about 30 minutes. About half way through, brush with a little more of the oil mix and flip. The taters will be crispy grilled on the outside, and creamy on the inside. Good with sour cream/chives or ketchup.
You can change things up by adding more/different spices. I am partial to my homemade chili powder.