Would you prefer slightly long handlebar for bikepacking?, TourDivide
The tour divide is a long event riding 10-20 hours a day for over two weeks.
Your biggest priority should be comfort, your bars should be set to a width that is most comfortable for you.  Any small amount of discomfort with the position after a 1 day ride will be much worse by 15 hours into day 3.
If you are fortunate enough that your body will tolerate and/or adapt to a wide range of positions, you should then think about how your bar width is going to interact with the rest of your kit.  For example some bar bag designs interfere with your brake levers if your bar is narrow.
And what about other accessories you may want bar space for (gps, power bank, tri bars, feed bags)?
Once you answered these questions you will have your answer.
And as is the nature with bike packing you may only find out what is going to work well for you after you've experimented in training.