Can customers choose the crust, the size and the toppings when they order pizza online?

Yes, through option groups on the dish. Under Menu, add a Size group marked Must pick, a Crust group marked Must pick, and a Toppings group with a Max picks number and a price on each topping. On the ordering page the customer answers each group in the popup and the price updates as they pick. The same rules are checked again on our side at checkout, so nothing can be skipped from a phone. A pizza ordering system is mostly getting these groups right once. The Menu & inventory tab in the docs has a guide called Add an item with extras and choices.