The synthesized 0.3(Ba0.7Ca0.3TiO3)-0.7(BaSn0.12Ti0.88O3) nanoparticles (BCST NPs) and their morphotropic phase boundary (MPB) evolution characterized based on the structural, vibrational, dielectric, and ferroelectric properties of the individual Ba0.7Ca0.3TiO3 (BCT), BaSn0.12Ti0.88O3 (BST) NPs. The MPB system had a dielectric constant/loss of 710/0.088 at 1 kHz frequency, with remnant polarization (Pr) of 8.5 μC/cm2, under a coercive field of 15 kV/cm at 1 Hz and its fatigue property evaluated up to 108 cycles. The BCST has a piezoelectric coefficient of 65 pC/N. Flexible polyvinylidene fluoride/BCST NP composite films (PBCST-CFs) were fabricated and characterized. The optimal loading of 15 wt% provided a more electroactive phase (70.93%), a dielectric constant of 33 and loss of 0.0066, and a Pr of 0.8 µC/cm2. The PBCST-CF (15%)-based nanogenerator (PBCST-CFNG) generated electrical output of 92 V, 440nA upon applied 8 N force under acceleration of 2 m/s2, with power density of 44 mW/m2 at 160 MΩ. Electrical poling, durability, and switching polarity testing, charging of commercial capacitors, and the driving of low-power electronics were also performed. A PBCST-CFNG (15%)-based piezoelectric ball was designed and used to monitor the ball height/distance, rotations, and impact positions/counts.