Hannah Montana was a Disney show where a girl was a popstar under a different name and wig so she could be a normal person when she wasn’t performing. VTubers, like Ironmouse that op referenced, are streamers that essentially play characters rather than stream as themselves in order to preserve their anonymity. They have cameras that track their movement, but rather than just stream the feed of the camera, they map that movement onto an avatar, usually a 3d anime girl.