This review provides a comprehensive overview of recent advances in the optimization and performance analysis of lead-free and inorganic perovskite solar cells, with a particular focus on CsSnCl₃, CsPbI₃, and Cs₂CuBiBr₆. Using insights derived from SCAPS-1D-based studies, this review highlights comparative trends between lead-based and lead-free perovskites, emphasizing the environmental advantages and emerging efficiency potential of non-toxic alternatives. Reported simulation data indicate that optimized device architectures—such as ITO/CeO₂/CsSnCl₃/CBTS/Au and ITO/TiO₂/CsPbI₃/CBTS/Au—exhibit distinct variations in photovoltaic parameters. Specifically, CsSnCl₃ achieves a Voc of 0.96 V, Jsc of 32.22 mA/cm², FF of 86.40%, and a PCE of 25.1%, whereas CsPbI₃, a lead-based perovskite, delivers a Voc of 0.997 V, Jsc of 21.07 mA/cm², FF of 85.21%, and a PCE of 17.9%. For Cs₂CuBiBr₆, a lead-free double perovskite, efficiencies range from 18.69% to 19.70%, depending on the selected electron transport layer. These results collectively demonstrate that lead-free materials can achieve competitive or even superior performance while offering improved environmental compatibility. Furthermore, the review discusses the influence of absorber thickness, ETL/HTL combinations, series and shunt resistances, and temperature on overall device operation. Overall, this analysis underscores the growing potential of lead-free perovskites as sustainable, high-efficiency alternatives fornext-generation thin-film photovoltaic technologies.