I just completed the race.  The scenery is amazing, especially the canyons, flowers and high-country: Nothing I ever would have seen if I had not done the ride.  Its probably the most beautiful ride I have done). 
I was really glad that I had the full suspension/had 130 travel and the dropper post.  There is some really fun single track, nice dirt roads but also some long steep hike a bikes (one is about 2 miles or more with over a  thousand feet of climbing) and rough terrain which was hard for me as I am not used to this, so I'm glad that I had comfortable shoes.  I also ran into some small mosquitoes which bit but did not itch, wished that I had some bug spray.  Other things:
-Loose rocks on the descents
-The Beef trail (drops into Shell) has amazing views and fun singletrack but also several technical exposed sections.  I would not ride the sections that are exposed with rocks or ride it at night.  Little Horn Canyon is also very beautiful but technical in spots so I would not this at night either
-I would bring lights just in case/everything took me longer than I thought it would as this ride is very hard; probable the hardest ride I have done (but it was my first bikepack race as well)
-I wished that I had bear spray.  I saw lots of bear tracks near Littlehorn canyon and also a herd of wild mountain goats at the bottom of Shell Canyon.  I wasn't sure if they were aggressive and so I just waited for them to get off the trail.  I also saw a dude from a local dude ranch on a horse with toxic masculinity. 

-I found that leaving my bike on full downhill suspension the whole ride helped me avoid saddle sores/except while standing