I’ve sent from 19 lb Niner RDO HT to a Spec epic 22 lbs to a Trek 100mm to a Trek 120 to a Scott Spark 120/130 and now to a Scott Genius 150/150 with a Fox 36 on the front. I have a Genius AXS build and swapped out the seat post and brakes for a lighter setup.
For me, I’m not fighting for a win in these races so it is more about my personal performance. I’d rather give up a little bit of weight, have one mountain bike to maintain, and have something that can rip in Moab or where I ride every day in Colorado. My race setup is with Stans Podium SRD wheels with Maxxis Aspen 2.4 tires and a XX1 Eagle cassette. The training setup is with the stock carbon wheels from Syncros, 2.6 Rekon tires, and a GX cassette. Probably not the absolute best tool for the job of a XC race but I prefer to race marathon anyway. I just did a 12 hour race and lapped faster than my last time on the course on this bike vs my 120mm Scott Spark.