No Remus on my RT (ever) but I had one on my XR1200. A real quality piece with one exception. The exception is that the weld on the rear header at the exhaust port was huge, actually reducing the ID of the pipe a couple of MM. It took some time to grind it down to match the port and header ID. That aside, the Remus pipe was the best made aftermarket exhaust in my limited experience, good welds, everything lined up well during assembly, really well made muffler, etc.
As far as noise, the XR (DB killer in) was just this side of my obnoxious line, far louder than the RT. My next door neighbor is a friend, she made a comment about hearing me come and go on the XR. Not loud enough to make her angry, just loud enough, in spite of my efforts to keep the noise down in my 'hood, she could hear me inside her house. Not scientific but I hope that helps you get an idea of the volume level.
Somebody will probably correct me but IIRC the the change between the older laws in Europe (what the Remus probably meets, DB killer in) to Euro V (what the new BMWs are built to meet) is about two DB, something like a 50% increase is sound energy.
How loud is too loud is up to you (and at some point your local police), good luck.
I have a Remus exhaust for sale in the classifieds.