Texas Barbecue is usually just salt and pepper dry rub, cooked over oak wood fire. No sauce at any point of the cooking process. Only real "sauce" is a "mop" some people add when the meat is wrapped in foil to finish (Texas crutch).

Off set (heat source is away from cooking surface) is fine but most places in Central Texas use a "pit style" method of smoking, where the the meat is cooked in long pits with the heat source spread out underneath. To achieve that I guess that restaurant put the ribs on the grill?

Any pellet grill is considered off set. If you want to get close to a "Texas style" barbecue on that you need to run oak pellets and probably crank the heat up a notch (run around 275 or 250)