yeah if you find that diffuse isnt working as emissive just make an emissive. I personally don't like using emissive for stuff like that as it's a constant strength, I much prefer ramping up the diffuse channel which will vary in strength depending on lightmap. You could derive perhaps a better emissive texture/glow by…
combining two normal maps can be achieved by going into the layer options of the map you want to mix in, disabling the blue channel (should be 3 checkboxes that say R. G, and G), and then set the blend mode to overlay. then controll the intensity with the opacity slider.
Yes, you can combine normalmaps. Put the one you want to combine in a layer over the base normalmap, set the blend mode to overlay, then go in to the Levels of that layer. Change the dropdown from RGB to Blue at the top, and the reduce the range from 0-255 to 0-128. Done! Best to make an action out of this, since you might…