Yes, all very different packs to be sure.
I use a Montane Grand Tour 55 (1.2kg ish) for lighter loads, but with loads anywhere over 13kg, it really does not carry as nice as it only has a single aluminium stay. It doesn't cause me issues with heavier loads , but I feel myself rejoicing when I start working my way through the consumables to get below that 13kg mark to increase my comfort. The backpanel on the Montane is solid foamy stuff (to give it some more rigidity I assume)and I do sweat like a mo fo on my back with it on.
Someone mentioned the Osprey Levity/Lumina series, I have seen one in action and I don't like the minimalistic looking hipbelt on the or the fact there are no hipbelt pockets, but those packs do tick your weight requirements.
My 34 lt daypack is an Osprey that has the AG system, same as the Atmos and Aura. My husband bought it for me and I thought it was a bit gimmicky but my oh my does it feel good on. I can really load it up and be carrying up around 10kg and it feels like nothing. For giggles at home I loaded it past the 13kg mark and it still carried nicer than my 'big pack'. It compresses down for the smaller loads nicely too. I love how the hip belts are integrated into the mesh suspension and dual stay system. I have no weight on my shoulders at all and it just feels like a 'hug'. My back sweats
so much less, which I appreciated when walking this week as temps were in single digits and it was easier to stay warm once stopped without a drenched back.
So, not really helping you as I am banging on about a daypack, but what using that AG harness system has done is caused me to want it when carrying a larger pack too, so yesterday I ordered a 65lt Osprey Aura for those heavier carries I do over the cooler months. I bought it in the most hideous, impractical colour I may add , as it was 43% off RRP and I am a tighwad . There are no hideous colours (all pretty nice really) on the mens equivalent Atmos, so you will be right and there are plenty of good deals around on 2017 packs. I paid $215 incl express shipping.
It is funny, as I nearly felt embarrassed to order the Aura, as it is very 'mainstream' and didn't feel like an imaginative purchase, but I have listened to my body and gone with something that feels great on for me. I am sure will get a lot of use, even if it isn't very fashionable or ultralight
I think when carrying heavier loads, a heavier pack is nearly an inevitability for comfort. Happy researching, I think that is half the fun of a purchase.
edited for typos