Do I need the POS add-on before I can connect Talabat?

No. Connecting the apps and answering their orders works from the dashboard on any plan. The kitchen screen is part of the POS add-on, so if you want your cooks to press Accept and Refuse on the wall screen you need that. Otherwise you answer from the Orders from the apps panel on the Delivery apps page. The Orders from delivery apps tab in the docs says what needs the POS.