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Wingtip devices are widely used on car and race-car rear wings to control the tip vortex and improve aerodynamic performance, yet their behaviour on inverted, low-aspect-ratio wings operating under a fixed width constraint is less well characterised than on aircraft. This study investigates how endplates and anhedral (downward-canted) winglets affect the downforce and aerodynamic efficiency of a rear wing based on the Selig S1223 profile. Five configurations were examined using steady-state RANS CFD in ANSYS Fluent: a baseline extruded wing, a wing with a rectangular endplate, and wings fitted with anhedral winglets canted at 20°, 45°, and 70°. Turbulence was modelled using the k-ω GEKO (Generalized k-ω) model. All cases used a constant 250 mm chord, an angle of attack (AoA) of 5.75° and a fixed projected half-span of 900 mm, so that every device was compared within an identical top-view footprint representative of automotive packaging limits (design/regulatory boxes). The two design objectives assessed were the generation of maximum downforce and the maximization of aerodynamic efficiency, defined as the lift-to-drag ratio. By isolating cant angle as the sole geometric variable across the winglet configurations and comparing them against both a bare-wing baseline and an endplate reference, the study aims to clarify when, and to what extent, each wingtip device is worthwhile for practical applications.