Multi-Plane Light Conversion (MPLC) coherent beam combining (CBC) presents a promising approach for flexible optical field manipulation, overcoming the limitations of low energy utilization and poor beam quality in traditional CBC methods. However, its potential for generating diverse structured beams and the underlying design principles remain underexplored. In this work, theoretical model of MPLC-based CBC system was constructed to perform numerical investigation on the property and capability of MPLC optical field manipulation. Localized phase coding and vortex phase coding methods were proposed for mode mapping design to enhance the match between input and output modes. By employing multi-dimensional evaluation metrics including conversion efficiency (η), side-lobe suppression ratio (SSR), and phase matching degree (PMD), the performance of different coding strategies was systematically compared. The results manifested that while random coding yielded an average efficiency of 92% for five multi-focus beams, both localized and vortex coding significantly enhanced output quality, achieving a superior average efficiency of 97.1%. Based on the proposed encoding methods, MPLC successfully produced 5 Laguerre-Gaussian (LG) beams, 5 geometric shapes, and 5 letter patterns with remarkably high average efficiencies, reaching 97.4%, 99.2%, and 96.5%, respectively, accompanied by high SSR (>14 dB) and PMD (>96%). Furthermore, a strategy for arbitrary beam shaping by decomposing the target field into a linear combination of orthogonal modes was proposed and confirmed using a 21-mode MPLC. Simultaneously, its flexibility and the consequential requirement for strong amplitude modulation on the laser array were discussed. Finally, the relationship between the number of supported modes and the required number of phase plates was also analyzed, illustrating that maintaining high efficiency for a larger number of modes necessitates a significant increase in the number of phase plates. This study effectively generated a wide range of structured beams with minimal stray light and high energy utilization, demonstrating that MPLC-based CBC is a powerful and versatile technique for high-efficiency, high-quality optical field manipulation. Future work should focus on optimizing the design to reduce the requisite number of planes, paving the way for practical applications in high-power laser processing, optical communications, and quantum optics.