Despite the fact that relaxor ferroelectrics (RFEs) have been extensively researched because of their various advantages, there are still barriers to simultaneously increasing their energy storage density (W-rec) and efficiency (eta). By substituting Bi(Mg0.5Sn0.5)O-3 (BMS) and optimizing the formation process, this study follows a stepwise optimization route to achieve comprehensive exceptional energy storage performance (ESP) in Na0.5Bi0.5TiO3-Sr0.85Bi0.1TiO3 (NBT-SBT)-based ceramics. On the premise of constructing a Sr2+-Sr2+ ion pair at the A-site to ensure a large polarization, the introduction of Mg2+ and Sn4+ ions at the B-site further induces a local disordered field and promotes polar nanoregions. Following that, the viscous polymer process (VPP) used to synthesize NBT-SBT-BMS ceramics can thin the thickness, reduce defects, and boost compactness, hence improving the polarization difference (Delta P) and breakdown strength (E-b). Using the stepwise optimization route, we were able to attain a high Delta P of 64.6 mu C cm(-2) and an E-b of 440 kV cm(-1) in 0.92(0.65NBT-0.35SBT)-0.08BMS-VPP ceramics. More crucially, an ultrahigh W-rec of 7.5 J cm(-3) and a high eta of 85% are simultaneously achieved, together with excellent temperature adaptability between 20 and 120 degrees C. Our superb ESP exceeds the majority of previously reported NBT-based ceramics, confirming the applicability of this stepwise optimization route to other similar high-performance dielectric ceramic designs.