In modern turbine blades, pressure-side cutbacks with film-cooling slots stiffened with lands and pin fins that are embedded in passages are used to cool trailing edges. There are many studies that have investigated these cooling configurations from a thermal perspective, while only a limited number have been concerned with the aerodynamic aspects. This study presents a thorough computational investigation of a film-cooling configuration to determine the optimum combination of shape and size of pin arrays. The analyses are performed to include both internal and external surfaces of the trailing-edge cutback region and the results are evaluated from both aerodynamics and thermal aspects. The internal structure of the configuration studied consists of staggered arrays of pins and airfoil-shaped blockages in front of the slot exits that open into a pressure-side cutback region. The pins used are of circular, elliptical, or airfoil shapes that are rarely studied in such configurations, and of different sizes, resulting in five different models for comparisons. The flow features, pressure losses and heat transfer characteristics inside of the trailing-edge surfaces and in the vicinity of the slots and on the external cutback region are examined. The airfoil-shaped pins are found to decrease the pressure losses in internal flow compared to the other pin shapes of similar size. However, the pin arrays produce minor differences in the velocity contours in the breakout region, resulting in similar pressure loss trends here. The small-sized pins are found to demonstrate slightly higher film-cooling effectiveness on the breakout surface due to lower temperatures at the slot exit. It can be inferred from the results that, since the airfoil-shaped pin reduces the aerodynamic penalty across the internal pin array, performing an optimization on the size of these pins to achieve the desired cooling performance could be a reasonable approach in the design process.