Optimize texturing

I’m looking for most optimized texturing method. I try to do RGB mask for materials align on model. See pics. I did some RGB mask to texturing two garage models. This RGB-mask materials use over 5 materials (or 8 in more complexity material). This materials are also using with other model in game (about 35-40 materials for all models). RGB masks for garages are 1024x1024, included materials have textures about 256x256, 512x512 (rarely 1024x1024).
If making textures in SubstancePainter - it need over 4k resolution for best view, but we loosing adjustability (power of dirt and scratches, colors…).
I’ve read, that game processing materials for once, and then apply it for each models.
Can you say, what more optimized - make RGB mask for universal materials using for each model, or make big unique materials (map, norm, spec…) for each model?