As far as wheels go, IME, it depends on your weight. I’m around the 90 to 92kg mark in full riding kit, and found Crest 29er rims quite flexy on rocky natural routes. The wheels in question had DT Rev spokes and build quality/spoke tension was good. In fairness they were fine on trail centre stuff like Dalby and 7 Stanes, it was on natural stuff around Edale and Hayfield (Peak) that they felt wibbly and vague. Also know other folk who are in 70 to 75kg weight range and they don’t have any probs with Crest wheels at all.
Gearing wise, I run 2×10 on my FS 29er and think it’s the way to go for general all-round trail use. Can’t recall exact set-up without looking, but think it’s 38/22 front with 36t max on rear.
HTH