GB: Yes, easy to differentiate between the two. A TR vibration is high frequency felt in the pedals. A MRB vibration is not high frequency and is not felt in the pedals.
Yes ....and possibly not. Not all main rotor induced vibes are 1P. Example: 4P main rotor on the S-70 is 17.6 hz while the tail rotor 1P is 19.8 hz. Hard to differentiate those two frequencies. It would help if only the pedals were shaking, but thats not always the case. The vib gear eliminates the doubt.