The structural peculiarities in hybrid perovskites (ABX3, where A=organic cation, B=Metal, X=Halide) often lead to a wide range of exciting electronic and optical properties with a consequent effect on the efficiency and stability of the optoelectronic devices based on these materials. The Rashba-Dresselhaus effect is one such consequence that has been prevailed in the hybrid perovskite family. The inherent spin-orbit coupling (SOC) effect in a non-centrosymmetric crystal structure of hybrid perovskite systems has laid the foundation of Rashba-Dresselhaus effect. This Rashba-Dresselhaus splitting directly governs the charge carrier recombination, which eventually controls the carrier lifetime and diffusion length and therefore the solar cell efficiency for such hybrid perovskite materials. In this work, we depict a vivid picture of Rashba-Dresselhaus effect in hybrid perovskites materials and the immediate implications in the field of optoelectronics. Here we have performed a rigorous structural search prediction of the mixed cation-mixed halide hybrid perovskites FA0.83MA0.17Pb(I0.83Br0.17)3 and FA0.875MA0.125Pb(I0.875Br0.125)3 which are the two nearest neighbor structure of record efficiency (22.1%) holder FA0.85MA0.15Pb(I0.85Br0.15)3 in the structural composition phase-space. We have found the prediction routes for such structural search as the mixed perovskite structure govern the Rashba-Dresselhaus splitting energy value, depending on whether it has been predicted from FPI or MPB as parent structure, which is leading to the mixed phase FA0.83MA0.17Pb(I0.83Br0.17)3 and FA0.875MA0.125Pb(I0.875Br0.125)3 respectively. The strong dependency of the splitting energy on the structural phase evolution along with the stoichiometry and space-group is also observed, wherein the mixed phase, 0.045 difference in concentration could lead to a remarkable difference in the splitting energy, which is more pronounced in the valence band as compared to the conduction band. We have also determined the Goldschmidt tolerance factor to envisage structural stability of the newly predicted crystal structure from both the chemical route in the composition phase space.