Perovskite solar cell (PSC) is a transformative step in advancement of photovoltaic technology as it presents the high power conversion efficiencies, cost-effectiveness, and customizable material properties. The theoretical investigations into mixed halide-based PSCs through computational perspectives are focusing on structural, electronic, and optical characteristics. Advanced simulation techniques, DFT (Density Functional Theory), SCAPS-1D, etc., have provided critical insights into the behavior of both all-inorganic and organic-inorganic hybrid perovskites under various conditions. For all-inorganic systems, simulations demonstrate exceptional thermal stability, tunable band gaps, and efficient charge carrier mobility, which are essential for developing durable and efficient solar cells. In organic-inorganic hybrids like MAPbI3, theoretical studies elucidate the stabilizing role of organic molecules and the impact of compositional engineering at the A-site and X-site on performance and stability. Key areas explored include defect formation, excitons dynamics, and degradation mechanisms that influence long-term device reliability. By integrating theoretical predictions with experimental data, computational studies play a prime role in material screening and performance optimization, paving the route for coming generation PSCs with enhanced efficiency, durability, and scalability. This review underscores the importance of theoretical research in advancing mixed halide PSC technologies for sustainable energy solutions.