This work presents a combined experimental and numerical methodology to investigate hydrogen–air flame propagation limits and consumption speeds in narrow Hele-Shaw channels. Experiments focus on flame propagation along the channel face, while two-dimensional Lattice Boltzmann simulations are performed within the channel gap, reducing computational cost while resolving transverse flame structure and confinement-induced effects. The results show that increasing the gap size widens the flammability limits and enhances the global consumption speed, primarily due to reduced conductive heat losses to the walls and stronger development of flame instabilities. Confinement plays a dual role: it modifies the balance between heat release and thermal losses, and it alters the growth of flame instabilities. To separate intrinsic burning behavior from geometric amplification associated with flame wrinkling, a normal consumption speed, $s_{cn}$, based on experimental flame length measurements in face view, is introduced. This quantity provides a physically consistent basis for comparison between experiments and gap-resolved simulations. The numerical approach predicts both propagation limits and with deviations below 5% for strongly confined configurations. It demonstrates that key deviations of flame propagation velocity to laminar flame speed arise from the physical effects acting within the gap and wrinkling in the face view. For weaker confinement, the local flame curvature is not dominated by curvature within the gap. As a result, discrepancies between the measured experimental $s_{cn}$ and the numerical gap-resolved consumption speed indicate the growing importance of curvature variations induced by face instabilities, thereby defining the validity range of the reduced modeling strategy.