A 115-120mm FM909 would be perfect. I don't think a 120/120mm FM1001 is a good combo, the geometry chart is with a 140mm fork and already has a 78deg seat tube angle. With a 120mm fork, it'd be close to 79deg, which doesn't match the geo for a 120mm bike well.
Neither is ideal for my requirements, both would be a compromise. The 1001 is going to be better for the long steep seated climbs here of 800-1400m that go on for ages. It's also going to offer more comfort on the equally long descents. But it'll lose out on the rolling sections, road connections and short, sharp out of the saddle climbs. The 909 higher slung shock also allows for 2 bottles and will avoid some of the huge amount of dust that will be thrown at the 1001 shock.
I'd prefer the 909, but with a little a bit of added travel at the rear for those 30-40 minute descents and rockier sections. It'd be a better tool for the job, hence wishing Carbonda / FlyBike would offer the 909 with a 'downcountry' rear triangle option. I think it'd be in their interests to offer it, since downcountry is the biggest growth segment in MTB and new N+1 besides eMTBs (like gravel is on the road side).