Mutant 38

None of them seems super comfortable, but also not unbearable at all. Ok, now we are getting somewhere. If they all feel about as easy / difficult / uncomfortable to carry, that is probably because you aren't used to the weight, rather than any specific variations in design. For example, the Osprey

I've never met you, I've not sized your pack / fitted it to you, or know anything about you. The Osprey is widely considered to be a pretty comfortable pack, for what it is. There's a couple of reviews below. https://www.outdoorgearlab.com/reviews/climbing/mountaineering-backpack/osprey-mutant-38 ht

The very popular mutant 38L is about 1.2kg, while the warthog 45L is about 760g - almost half. Ofc the osprey might be comfier and have more structure to carry very heavy weights (unlikely with only 40L ish), but imo I can’t justify almost double the weight for that. That’s ofc up to you to determin

I love my Osprey Mutant 38. The bag is designed really thoughtfully with all the storage arrangements, the material feels very durable and premium, and the weight distribution + strap cushioning feels very comfortable, especially on summit day pushes.