Hello all!
@Noel : Thanks for the tip. At first it didn't work, freezing my BIAB. But then I realized my song was x3 (repeated 3 times) so this + the master combining all the instruments was the cause. I put the song to only play once and dragged and dropped the drums first then the bass (I don't need the other instruments, it's just to give me an idea of the final products but I'm gonna play all the guitars). Doing so, dragging one instrument at a time only took 1mn or 2 max to display in Reaper. So this solution does the trick. BUT, it's a pain in the butt and I shouldn't have to do that since there is the BIAB vst plugin. So while I can now record this is still disappointing.
@Pipeline : thanks for your help. Yes I made all the changes using F5/bar settings (to my knowledge this is the only way to input RT&RD changes anyway) so I don't understand why it gets messy through the BIAB vst plugin. What happens is that I have a RT A which is played ok, then it switches to RT B as it is supposed to, but this is where it gets messy since the plugin stay within that second RT and doesnt aknowledges any more changes (3 others). I don't understand why the plugin partially gets the arrangement. I will look into what you put to download in your post, didn't have a chance to give it a go so far.
Apparently I'm not the only one having issue with the VST plugin and another member (read here :
https://www.pgmusic.com/forums/ubbthreads.php?ubb=showflat&Number=573356&gonew=1#UNREAD ) had issues as well and he pointed out one of his past thread where others as well did encounter issues. This is something which HAS to be resolved by PG. There can't be a Daw vst plugin not working properly if you have many changes in styles or drums.