I think there might be a lot of variation here, both by region and perhaps by individual restaurants. For instance take-away, take-out, pick-up and to-go are all common terms. Also restaurant language is quite concise.
For context, it would be useful to know who is talking to whom. I’m assuming below that someone is talking with the manager.
What types of customers does this restaurant mostly consist of? Dine in, takeout or delivery customer?
What types of customers do you mostly serve? Dine in, takeout or delivery?
What is the main type of orders for this restaurant? Dine in, takeout or delivery customer?
What are most of your orders? Dine in, takeout or delivery?
Who are the main group of customers for this restaurant? Dine in, takeout or delivery customer?
See. #1.
The main customers are takeout and dine in customers.
Most customers dine in or order takeout.
The restaurant has many passerby/passing customers. (Can passerby/passing be used in this sentence?).
The restaurant has a lot of foot traffic outside the door.
(The term “passers by” is quite a mouthful.)