Numerical analysis of impinging jets is widely recognized as a highly challenging task that requires careful consideration. With imposed flow features being the primary mechanisms that drive the production of intense turbulence. Those can only be accurately captured through computational models with the capability to appropriately resolve turbulence fluctuations. These mechanisms are particularly associated with the shear layers induced by jets emerging from a nozzle into a quiescent fluid and the arising shear region between two parallel jets. Both regions are part of the wall-bounded impingement region. This study presents a numerical investigation of perpendicular impinging-jet configurations composed of parallel twin jets. The first configuration, referred to as the Double Square Impinging Jet (DSIJ), features a nozzle arrangement resembling two three-dimensional ducts positioned side by side. The second configuration, termed the Double-Slot Geometry (DSG), is derived from the DSIJ setup by imposing spanwise flow homogeneity. Adding a species to the flow or creating local temperature sources supplements additional scalar transport equations. Conventional and sensitized Reynolds-Averaged Navier–Stokes (RANS) approaches are applied to examine mixing processes, employing Reynolds Stress Model (RSM) formulations to describe the underlying turbulence dynamics. The study focuses on an eddy-resolving Reynolds stress turbulence model that governs the entire subscale stress tensor, as proposed by Jakirlic and Maduta (2015). Its formulation is derived from the conventional near-wall RSM and is specifically designed to enhance sensitivity to turbulence fluctuations. This sensitivity is achieved by incorporating a production term in accordance with the Scale-Adaptive Simulation (SAS) concept, which was introduced by Menter and Egorov (2010). All results are benchmarked against a Large Eddy Simulation (LES) using a wall-adaptive local eddy-viscosity model (WALE) (Nicoud and Ducros, 1999). The analysis focuses on key flow quantities, such as velocity fields, Reynolds stress components, and scalar mixing characteristics. Particular emphasis is placed on modeling turbulent scalar fluxes.