Throughout my career I have been tasked with creating 3d models for various game engines. Nintendo required extreme low poly with separate textures. As the industry grew I used Atlas sheets to keep textures together. Today I are using layers to create complex textures (Height, Roughness, Metallic, Normal, Albedo, and Detail Albedo, Gloss, AO). Mega Scans and Substance Designer and Painter have helped increase the speed and complexity for interesting and exciting texturing, responding to reflection and light probs along with HDR and PBR.