The confined impinging jet reactor (CIJR) has emerged as a critical device in the production of lipid nanoparticles and other advanced materials, owing to its superior ability to achieve rapid and energy-efficient mixing. Among the key design parameters, the incidence angle between opposing jets plays a decisive role in governing flow dynamics and mixing performance, yet its effects remain insufficiently explored. In this study, a combined approach of large eddy simulation (LES) and micro-particle image velocimetry (micro-PIV) experiments was employed to systematically investigate the influence of incidence angle (0°~30°) on the flow field characteristics and mixing efficiency of CIJRs across a wide Reynolds number (Re) range (90~800). The results revealed three distinct flow regimes—separated flow, transitional flow, and chaotic flow—across all configurations. For Re<400, smaller incidence angles promoted an earlier transition to chaotic flow, yielding more vigorous vortex formation and enhanced macroscopic mixing. However, at Re≥400, larger incidence angles improved flow stability, constrained stagnation point oscillations, and promoted more homogeneous mixing over time. Notably, at α=30°, the inlet jets exhibited a wavy profile induced by wall confinement and recirculating vortices, which further intensified macroscopic mixing, although excessive confinement tended to restrict vortex development at higher Reynolds numbers. On the microscale, increasing the incidence angle improved spatial uniformity of mixing but was accompanied by longer micromixing times, reflecting a trade-off between mixing intensity and efficiency. These findings highlight that the incidence angle acts as a tunable parameter for regulating mixing performance in CIJRs. Overall, this study provides fundamental insight into the interplay between inlet geometry, turbulence dynamics, and mixing characteristics, offering a theoretical basis for optimizing CIJR design and operational strategies in chemical, pharmaceutical, and materials engineering applications.