Is it possible to use both BBCSO and one of the internal Playback Templates., like Iconica, in the same piece? If so, is there a tutorial that can help?
One can make custom Playback Templates that (say) tell Dorico to have the strings play through VSL and the rest of the instrument through Kontakt. So the answer to your question is “yes.”
John Barron did a Discover Dorico on it that would now be somewhere int he Dorico channel on YouTube.