The recommend setup is:
Fibre Broadband Installation with a Wifi..
2 Pcs/Laptops/Pads with HDMI outputs, one in the kitchen and one by a hosting station or till point. They should also have sound enabled as the system alerts when there are orders or a guest uses 'Call the Waiter' feature.
Mobile phone if using WhatsApp for ordering, usually with the Manager or Head Chef.
Depending on budget, having a large screen in the kitchen for viewing the Order Page improves efficiency.