cats material combiner isn't very good, i suggest learning how to manually bake textures if you want to keep stuff like normal maps and roughness.
now here's the fun part, 2.80+ removed the ability to bake transparent textures. you have to either bake the alpha to a separate texture (usually by abusing emission) and then combine them with GIMP/Photoshop, or be a 2.79 chad instead.