I was in the Kifaru show room two weeks ago specifically to try on the packs and was told the new duplex frame can not be shaped or changed to fit your body. Rep said it was the old frame that could be shaped. This was unfortunate because I defiantly have a sway back. I had tons of space between my body and the pack, both at the lower back area and again at the shoulders. On the plus side they offer different lengths. I tried on the 26 inch frame and the load lifters with 80lbs were a little low relative to my shoulders. Rep said they are working on a 28 inch which I might want to consider. But it's not out yet.
The Kifaru was not the most comfortable pack I've worn. It's really stiff and almost more like an external frame pack. So yes, it can haul weight. Very flat vs contoured. They also use pretty heavy materials and have more straps and Mollies than I need. Not bad, maybe that's what some guys want, but this also adds weight. People love the hip belts, but honesty I felt it wasn't any better than my Northface mountaineering pack. Kifaru is still in consideration, but I want to try EXO and Stone Glacier before deciding.
I tried Kuiu last week as well. I liked the lighter bag material. Plenty strong and durable. The frame fit me better because it has a little more contour and the stays flexed to my back under load. Stays sat a little higher too, offering a good angle for support. Hip belt was similar to Kifaru (icon pro belt), but the pack put more pressure on the lower lumbar. Took awhile to get it comfortable and still not 100% sure it would stay comfortable for the long haul.
After going through this I really believe fit is a huge component and like boots, everyone is different. So I would try before you buy. Or buy them all knowing you'll keep one and return the rest. It's a lot more expensive, but you'll be glad you did and won't have any doubts come next fall.