Hi Rikky!
The Special Edition sound set covers the standard and extended instruments (including the chamber strings).
For Sibelius it isn't important if the string ensemble is in fact an orchestral or a chamber string sound. In both cases the program violin (or viola, cello, doublebass) ensemble will be the one to choose. Just be careful that you load the right matrices in Vienna Ensemble and get the channels right.
Be careful with the Solo Strings. In order to to get the Sound IDs right, Sibelius needs to have the Solo Violin (Solo Viola, ...) staff. Violin 1 or Violin I is for String ensembles and will lead to Sound ID confusion with Solo Strings and therefore wrong or not happening articulation changes.
Best,
Andi
Vienna Symphonic Library