A series of monolayered lead halide hybrid perovskites (HO2C(CH2)n−1NH3)2PbX4, named (Cn)2PbX4 (n = 4–6, X = Cl, Br), exhibiting a low congruent melting temperature (Tm) (Tm = 130 °C for (C4)2PbBr4), high stability in the molten state, and whitish type emission, are reported. From the synthesis in the molten state, rare solid solutions of mixed organic cations (Cn1–xCn′x)2PbX4 (n, n′ = 4–6; X = Cl, Br; 0 ≤ x ≤1) as well as solid solutions of mixed halides (Cn)2Pb(X1–yX′y)4 (n = 4–6; X, X′ = Cl, Br; 0 ≤ y ≤1) have been prepared and characterized (thermal behavior, powder X–ray diffraction (PXRD), photoluminescence properties). The impact of substitutions is significant on the thermal properties, lowering the Tm down to 100 °C for (C4)2Pb(Br0.25Cl0.75)4. The emission properties are slightly tuned in the case of mixed organic cation systems, whereas modifications are more dramatic in the case of mixed halide systems, leading to emission properties through the entire visible region. These results illustrate the great opportunities offered by the congruent melting properties of halide perovskites allowing syntheses in the molten state.