here is an example on bricks. He puts some map on bevel to give it variety, and also to the mortar input later on the video.
About the math nodes, well they are not only for the inputs I mentioned above, more like for using math expression on maps. For example, how can I make a star shape appear only on white parts of a perlin noise? I would probably multiply star shape with the noise. I tried doing it with blend node but I'm not sure if that's what I actually mean. I am no expert of procedural texturing, but I feel like something is missing without having Add, Subtract, Multiply, Divide like we have on Blender, Unreal Engine and Unity etc.
Wish the trial of explanation wasn't too complicated, as to me what I said did not make much sense :')