I used this back when it was called the texture pack combiner. It doesn't inherently affect GPU usage or VRAM, it's what you put into the combiner that will determine that. I suggest making sure you know exactly what you are combining before going through with it. On my old rig, I popped in just about every pack I could, and let the combiner decide for me, and in areas where they used a lot of Serious HD Retexture stuff, I would have major issues. If you have a great computer though, it's an amazing resource and can save you hours of research trying to figure out which mods you should have overwrite one another.