Best way to do materials for Customization w/ guns/others (Substance Painter)

So I’m making a high intensive 75 player game, and I need the most optimized game possible, in the past I’ve used atlas textures and such… But this time I plan on having complete custimization, so like different, barrels and lengths, different recievers for each gun, ect, coming in total 12-14 parts for each gun, and then of course attachements (Which I’m going to do with 1 atlas texture) For the guns & parts, I’m going to need to have wetness effects, wear and tear over time (Which will connect to the data-base) and then of course weapon skins (Like CS-GO), along with the default textures, In total I’m going to have 40-50 guns, as I have some done already, with a few custom parts.
Now should I be using decals, atlas textures, or what else.

Also, so I plan on making default materials/instances where I can just place them to certain parts of my object, and make them multi-use which in theory would save performance (Please tell me if this is true), but I would like to have it to where I can place those materials, and also add Normal maps… Can I do this somehow?

FYI, I’m using Blender, Substance painter/designer