A newly popular technology being utilized to produce hydro energy from low-flow streams is the Savonius-style hydrokinetic turbine (SAHT). The different blade design modifications have recently improved the performance of SAHT. But due to its negative torque generation, harnessing energy from low stream speed with such type of turbine is quite difficult. In this study, an unsymmetrical aerofoil-based curve profile connected with a straight-blade segment with a combination of overlapping, straight edge gap, and straight offset gap, along with arc curvature at the blade tip is compared and analyzed in terms of flow structure interactions. The better aerofoil profile of a higher lift-to-drag coefficient ratio is considered in the present study. Specific design features like straight offset gaps of (5–20) mm and arc curvature of 4 mm are investigated, and fluidic behaviors are compared through flow structures. Performance characteristics are compared at a low flow stream speed of 0.4 m/s, commonly found in low-discharge channels. Results show that the unsymmetrical NACA 63415 curve profile, out of all the considered straight offset gaps, has shown a maximum torque coefficient and output power of 0.75 and 1.47 W at a 15 mm straight offset gap. In addition to this, well-developed flow structures in the overlapped portions, duly contributed by the straight edge gap, offset, and arc curvature at the blade tip increase the flow interactions on the suction surfaces and at leading and trailing edges, which contribute to increased overall performance on the turbine.