This study presents a direct numerical simulation (DNS) investigation into the interactions between pressure-driven and thermally driven turbulence in mixed convection flows. By systematically varying Reynolds and Prandtl numbers, we examine how weakly diffusive thermal fluctuations influence energy transfer and turbulence production across scales in a periodic channel configuration. The results reveal that while large-scale convection rolls dominate global flow dynamics, their coupling with pressure driven turbulence is highly dependent on thermal diffusivity. Lower thermal diffusivity (higher Prandtl number) confines thermal activity to smaller scales, reducing its influence on pressure-driven mechanisms and altering the spectral energy distribution. Detailed energy budgets show that multi-physics interactions in mixed convection do not create sub-Kolmogorov turbulence but significantly reshape turbulence production pathways. The spectral analysis further confirms that thermal effects remain confined to larger structures, and the Batchelor scaling holds for temperature fields. These findings suggest that Reynolds-averaged Navier-Stokes (RANS) or large-eddy simulation (LES) models require tailored treatment of the two-way thermal momentum coupling for accurate prediction in stratified flow environments.