Triply Periodic Minimal Surface (TPMS) lattices produced by Laser Powder Bed Fusion (L-PBF) using AlSi10Mg were examined to assess their mechanical performance and structural reliability. This study focused on Face-Centered Rhombic Dodecahedron (FRD) structures, including both uniform and functionally graded variants (FRD-30, FRD-40, FRD-45), and compared them with Gyroid and Fischer–Koch–S topologies, all designed with a relative density of 45%. Quasi-static compression tests carried out in accordance with ISO 13314 standards revealed that FRD-40 provided the highest elastic modulus, reflecting superior stiffness and load-bearing capacity. In contrast, the Fischer–Koch–S design achieved the highest total and specific energy absorption, coupled with a uniform defect distribution and minimal pore volume, making it well-suited for energy-dissipative applications. FRD-30 further demonstrated stable deformation and smoother stress–strain behaviors relative to its uniform counterparts. Defect morphology and internal porosity were characterized through high-resolution X-ray computed tomography (XCT), while fracture surface analysis by Scanning Electron Microscopy (SEM) identified delamination, unfused particles, and localized porosities that contributed to crack initiation and propagation. Finite Element simulations successfully captured the experimentally observed deformation and stress localization, validating the predictive power of the numerical models, while the Ashby–Gibson framework established density–property correlations and explained deviations caused by geometry and process-induced defects. Collectively, these results highlight how functional grading and topology optimization can improve the structural efficiency of AlSi10Mg TPMS lattices, offering valuable design strategies for demanding aerospace, automotive, and biomedical applications.