So I recently bought an NR reader and I noticed that it has no JPN-USA switch on it. Does this mean it's a PAL NR reader? Does it make a difference?
Yes it's a PAL model, it means its locked to PAL mode so it's equilivent to a normal PAL GC internally and software wise, with the difference being the NR-Drive.
That amazing mod can't switch either to PAL, or from PAL. Still highly recommended in my opinion (if one's GC supports it).
You could put the optical drive into any retail NTSC Gamecube if you are needing it to read NTSC NR discs but as it stands it will only read PAL NR discs.
