This study presents a comprehensive framework for the design, optimization, and simulation of lead-free, all-perovskite tandem solar cells, modules and arrays. Three environmentally benign and structurally stable perovskite absorbers CsSn₀.₅Ge₀.₅I₃, Cs₂TiBr₆ and Cs₂SnI₆ were systematically investigated using the SCAPS-1D simulation environment. The optimization of single-junction devices involved the strategic engineering of charge transport layers, fine-tuning of absorber layer thicknesses, and reduction of defect densities, resulting in power conversion efficiencies (PCEs) of 15.73%, 9.4% and 15.48%, respectively. A complete screening of 48 device architectures was performed, encompassing 16 distinct hole and electron transport materials (HTLs and ETLs) for each absorber. The most compatible transport layers were identified and integrated into the corresponding device structures. Subsequently, two four-terminal (4-T) tandem configurations Cs₂TiBr₆/CsSn₀.₅Ge₀.₅I₃ and Cs₂TiBr₆/Cs₂SnI₆ were designed in accordance with the Shockley–Queisser efficiency limit, achieving initial PCEs of 25.13% and 24.88%, respectively. The reported values were obtained considering that the voltage and current of the absorber sub-cells in the tandem structure are completely independent. Upon finalizing the optimized tandem cell architectures, corresponding perovskite modules and arrays were developed to deliver input power to a multi-string inverter, a configuration widely adopted in residential photovoltaic systems due to its high performance and flexibility. Among the studied configurations, the tandem architecture based on CsSn₀.₅Ge₀.₅I₃ exhibited superior performance, which is attributed to its enhanced spectral utilization and optimized energy bandgap. These findings highlight the considerable potential of transparent, lead-free perovskite modules for sustainable and aesthetically integrated applications, such as building-integrated photovoltaics.