For those of us with less then stellar pc's is there a way to get rid of everything besides the note highway like GH3 back in the day?

You can turn off a lot in the options menu (i think the only thing that is permanent are the speakers.)

You can disable "venue mode" in settings, but I think there's still that room in the background.

 

There's also a bug in which backgrounds graphics don't come back if you restart song while in Riff Repeater, but that doesn't always happen.