I have used the MR nice frame with the crew cab, longbow, and then the metcalf bag when it came out. Really liked the idea of the crew cab bag and really wanted it to work for me, but ended up selling it as it seemed to be a 'jack of all, master of none' bag. When filling it, it filled out away from your back and to the sides. To get the load to go higher, you needed some type of dry bag or stuff sack, and then it seemed like it kind of defeated the purpose of the design of the crew cab bag. Why not just get a different pack bag that is an actual 'bag'. Even when using it to pack (elk) quarters, the weight always seemed to ride too low. I'd do my best to cinch up the weight above the hip belt, but the design of the pack made it difficult to do that, and I never discovered a way to make the bag ride higher on the nice frame. I used it with and without the 'lift kit' accessory to raise up the load lifter straps. It rode better with the lift kit, but still had the issues described above.
For me, I found that I like an actual pack bag to put stuff in to keep the rain, snow, dust, etc off and to contain all my stuff. Also, like everyone usually says about MR packs, it was heavy. I really wanted to like it and use it for a day pack where I could go out light and be able to pack an elk quarter or more back out, but when my base pack weight was ~8lbs before putting anything in the pack, my day pack weight jumped significantly.
I think the NICE frame (with lift kit) is very comfortable for me, and I still have the NICE frame, Longbow bag, and Metcalf (although I haven't used them in a while except as meat haulers and the metcalf as an overnighter/multiday pack) due to getting a lighter pack for day hunting.
I really like the layout of the Longbow bag. I feel like it was designed for me, but the overall base weight of the pack give me pause to grab it for a day pack when there are other options out there that do the job at almost half the pack weight.
Good luck with your decision!