I'm not sure if I completely follow. A few things come to mind.

Re: Is there some way to tell Realtracks to start at "certain offset position" at specific bar?

You can mute any one of the RealTracks and also un-mute at any bar. This is done by clicking on the bar and pressing F5 function key. The dialog is self explanatory. That will allow your RealTrack to start at any bar.

As for starting at an offset at a specific bar, you can insert a rest by entering the chord followed by a single period. E.g. if you wanted the RealTracks to start on beat 3 of the bar, enter as |C. C |

if you want the track to start playing at beat 2, enter as |C.,C |

If you generate and get the correct 'feel' you can freeze the track so that it won't regenerate next time you start the song. Freeze by clicking the small asterisk on the mixer, alongside the mute and solo button.

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