Hydrokinetic energy harnessing technologies are steadily acquiring the center stage of the modern renewable industry due to certain merits over the others. Significant research funding is being granted to institutions worldwide for optimizations and innovations in existing hydrokinetic devices. This numerical study focuses on one of the drag-based hydrokinetic turbines (HKTs) which has the potential to be a fitting choice for small-scale power conversion. A commercial solver in combination with the renormalized group (RNG) k-ε turbulence model is used to solve the unsteady Reynolds-Averaged Navier -Stokes (URANS) equations. The investigation highlights the role of the upstream deflector in exhibiting exceptional energy conversion efficiency by the HKT. Furthermore, the influence of flow velocity variations and differing blade profiles on the overall performance is also studied. In addition to analyzing the performance parameters, discussions on the flow behavior around the HKT blades are also presented. The results reveal that the use of deflector enhances the performance of the system by improving the efficiency up to 31%. Similarly, amplification of the incoming flow velocity has a positive impact on the torque generation and subsequently the power harnessing ability. From the various blade profiles simulated, the turbine with a rotor drum diameter (DR) of 0.25 extracted greater power output compared to the others including the conventional blade.