Regarding getting the height down - I am 6'2" and ride the size large. Since this is my first 29er I did have some struggles getting the front of the bike to feel right and most of that had to do with the front starting out too high, and maybe having too much weight over the front. I originally had a 90 mm stem angled up at 6 degrees and a 120 mm fork. This definitely made things too high and it was obvious that was the problem. I used the one fork spacer I had to lower the travel 15 mm, and also turned the stem to angle down. This felt better but for some reason I felt like the bike then had even more wheel flop despite being less slack. I eventually realized that having the stem upside down actually moves the bars forward (about 7 mm in my case) effectively feeling like a longer stem. It's worth noting that my bars have 8 degree sweep and no rise, whereas bars that I'm used to have a 9 degree sweep and 4 degrees of rise, which is easy to overlook but was making about a 8 mm difference in reach as well. The sum of these changes was about a 16 mm longer effective reach than my normal setup of stem and bars. So I went and bought some nylon washers and created another 12 mm or so of ghetto fork travel spacers, and I bought an 80 mm stem. After lowering the fork even more, and ending up with an axle to crown of 500 mm, I put the 80 mm stem on and it felt much, much better. With or without a spacer under the stem (which was now angled up) it felt good and so I knew I had finally gotten the right height and reach. I ended up only using a very small stem spacer (1.5mm).
In regards to climbing, well this is a hardtail so efficiency is a nonpoint imo. As far as geometry goes the chainstays are adjustable so even though part of the idea is to have them short, its not like they have to be. You could adjust them to be longer if you wanted the bike to do steep, seated climbs better. Even when they're slammed forward you're looking at a chainstay length about the same as a normal 26er, so if you didn't get front wheel lift on your 26ers, then you can definitely avoid it on this frame. The second thing working in your favor is the pretty low bottom bracket height. This makes your center of gravity low which fights the tendency to go over the bars OR have front end lift up hills.