Hybrid lightweight structures increasingly combine cast, wrought, and additively manufactured aluminum alloys, but the mechanical response of their welded joints remains strongly material-dependent. In this study, cast EN AC-42100-T6, wrought EN AW-6082-T6, and laser powder bed fusion (LPBF) AlSi10Mg stress-relieved plates were welded in 4 and 8 mm configurations using cold metal transfer and pulsed multi-control processes over two campaigns. Weld defects, microstructure, hardness profiles, and tensile properties were analyzed using a framework combining a hardness derived local yield-stress descriptor (σ_y,loc), a cumulative hardness deficit (ID_HV), and a porosity increment metric (ΔP). The second campaign eliminated fusion and penetration related defects, but did not mitigate fusion zone porosity in LPBF-related joints, which reached 13.7% in the 8 mm LPBF–Cast joint. Hardness analysis showed the widest hardness-affected region in the wrought alloy, an intermediate response in the cast alloy, and localized alteration in LPBF. Tensile results identified three degradation modes: strength loss associated with heat-affected zone (HAZ) softening in wrought-containing joints, ductility limitation associated with the initial cast condition, and porosity-associated ductility loss in LPBF-related joints. The lower yield strength reduction in LPBF-related joints does not imply improved performance, as fracture remains strongly influenced by fusion zone porosity. The results support material specific mitigation and design strategies for hybrid welded aluminum structures.