<p>Immiscible fluid flows involving Casson micropolar and micropolar fluids are crucial in various engineering and industrial applications, including biomedical engineering, food processing, lubrication technology, and polymer processing. This study presents a comprehensive model and computational simulation for unsteady, unidirectional, laminar magnetohydrodynamic (MHD) flow of Casson micropolar and micropolar fluids in a horizontal channel with a stable interface, inspired by the relevance of non-Newtonian duct flows. The modified cubic B-spline differential quadrature method (MCB-DQM) is employed to solve the governing partial differential equations under a constant pressure gradient and no-slip boundary conditions at the channel walls. The method is validated by comparison with the RBFPS method, confirming the reliability of the present computational approach. The study presents a novel investigation of unsteady magnetohydrodynamic (MHD) flow involving two immiscible fluids. The study uniquely integrates dual non-Newtonian layers, electromagnetic slip mechanisms, and interfacial thermophysical interactions within a single framework. A detailed parametric analysis examines the propagation of physical effects across the immiscible fluid regions, highlighting their hydrodynamic interdependencies. The analysis further highlights the combined influence of magnetic, inertial, and thermal parameters on velocity, microrotation, temperature, and heat transfer characteristics. The study also explores the skin friction coefficient and Nusselt number, offering valuable insights for the design of more effective and efficient systems across diverse applications.</p>