If you want grip on the descents it will be more about having a soft compound than big knobs. The course can be very wet, almost always with a rocky bottom (but not quite always). A lot of the loose stuff is slatey shards which are just slithery wet or dry. If you want a fast overall time, go for a fast xc tyre, but with volume for the fast rocky descents. You will be on your hardtail if that is the case obv.
I ran a Nobby Nic front/Racing Ralph rear last year on my hardtail and made the cut-off for the first time ever, they worked OK. The big rubber some of the guys above are talking of would definitely drag on the fire-roads, but make the descents more fun. Or less “interesting” depending on your POV.
I am going to take the full sus this year just for a change and won’t be too concerned about speed. I may put the NN/RR combo on that as the alternative would be Magic Mary/ Hans Dampf, which is a bit ott. Or I could buy some new summer tyres for it. Or just run whats on there and sod it. Probably the latter.