Polymer nanocomposites boast complex microstructures with instant control of final performance, including mechanical strength, thermal stability, and crystallinity. Although tremendous studies have been devoted to understanding the structure–property relation of polymer nanocomposites, the effect of simultaneous nanomaterial contents on binary polymers remains unclear. Here, we report how the microstructure and rheological characteristics are subject to change upon adding a hybrid multi-walled carbon nanotube (CNT) and graphene nanoplatelet (GNP). We choose a refined binary system based on polypropylene (PP) as a commodity polymer with proven long-standing applications, alongside ethylene-butylene copolymer (EBC) with a random ethylene and butylene monomers orientation for better impact strength acquisition. Rheology and microscopy imaging support an adequate dispersion of both materials across the PP/EBC blend, similar to when a single-particle nanocomposite is examined. Beyond investigating the heterogeneous nucleation role of CNT and GNP, the crystallinity rate and the half-time parameter for completing the ordered transformation are calculated using the Avrami equations. The thermal stability as well as the mechanical properties of all nanocomposites reveal improved resilience under heat and external stress, leading to a rising trend in decomposition temperature, tensile strength, and modulus.