<< But please explain whence the RT MultiRiff edits are copied and then pasted to the other RT? >>

Assume your style has a RT3363 acoustic piano track
Generate a RT3363 acoustic Piano Track on Utility Track #1.
Open the Audio Editor and select the Legacy Track #2 Piano Track you created Multiriff edits. You'll see the WAV form for that track.
You can copy/paste between the two tracks.



<< There is also one other issue that your help doesn't entirely address: regeneration. Regardless of MR edits, how do I know/ ensure that duplicate RT will have the same generated track unless each time before the initial playback I've already inserted it? >>

That's correct. The two tracks will not be exactly alike except for the edits you made. If you want to retain the exact track, you'll need to either make a copy or freeze the track. If that's the case, you can make a note of the instrument a new style will place on that track and leave the edited track frozen and generate the other instrument on a Utility Track and obtain the same result.

BIAB 2025:RB 2025, Latest builds: Dell Optiplex 7040 Desktop; Windows-10-64 bit, Intel Core i7-6700 3.4GHz CPU and 16 GB Ram Memory.