We are a staff cafeteria with a fixed price set meal. Does a cafeteria POS like this suit that?

Yes, and it is one of the simplest setups. Make the set meal a menu item with its price, and add an option group for the choices, for example Rice or Bread, marked Must pick. Put it in the Most sold tab under Settings → Arranging the POS so it is the first button the cashier sees. If you run house accounts for departments, the cashier picks House account on the Charge screen and the department settles at the end of the month. A cafeteria POS lives or dies on speed, and a one tap set meal is as fast as it gets. The POS and the counter tab in the docs covers the selling screen.