Not done this race but did the Transalp last year which is the same kind of thing (multi-day stage race). Not sure how the trails compare…
We used hardtails (Kinesis Maxlight XC Pro 2) for the sake of simplicity and easy maintenance and it proved to be a good choice in that respect with zero mechanicals. You do get pretty beat up, but if you've done all the training on the same bike then you are kind of used to it. Crucially, ride the bike you're accustomed to and make sure everything fits and works and can be relied upon. The only way to get to know the bike is to spend many, many hours on it in the months leading up to the race.
Good luck!
Transalp blog is here if you have a spare few hours ;o)