I've got an exped lightning too, also a bit of a bony spine. The metal stay that mole mentioned is easy to form away from any contact with your back and the bag itself is very adjustable to different back lengths.
my wife uses a (heavily home modified) Mindshift Gear OutBound holster to haul around her ridiculously heavy DSLR and lens.
Two bachelor clips on the shoulder straps and two side stabilizer straps seem to get the weight reasonably well balanced.
I think you will struggle to find better bang per buck than that. I have one and recently went through mental gymnastics trying to find something better having convinced myself that I needed more external pockets and might be able to shave 400g of my base weight with a different pack. In the end I couldn't find a clear better pack for my needs. On my back this pack fits in such a way that there is a small air gap over much of my back and I like that.
There is one very dubious Youtube video in which the person who made it says it wouldn't fit him. It nearly put me off but having got one an adjusted it properly I can't understand what he is on about.
Have a look at this one instead on how to fit the pack properly and you will see what a great system it is. Most of the load is carried on the hip belt and I've found that 12kgs is a very comfortable load all day. I've reduced my base weight by 2kgs now so expect to be even more comfortable on my next multi day hike.
I recently took an Exos 48 on the Via de la Plata. Was great, it's got a proper frame and trampoline. I needed to carry a lot of water some days and i appreciated the trampoline in hot weather. I really like the side entry for the side pockets, can put a couple of water bottles in each side and get at them easily. Nice stretchy pockets. Downsides would be the faffy and pretty feeble compression straps, they do work but not that well, I wouldn't want to be regularly attaching lots of things to the outside. No hip belt pockets. Can't think of anything much else to say negatively about it, lightweight, relatively cheap, good features, comfy for me. It's not really a bag that you're going to pass on to your kids, it's not going to survive that long.
When I got back from Spain I did notice the stitching attaching one of the hip fins was coming out. I've no idea if this was my fault in overtightening (I've ripped hip belts before doing that) or some issue with the bag. I got in touch with Osprey and they ultimately replaced it basically hassle free. I'd put 750 miles on that bag and they gave a me new one for nothing, can't say better than that.
I've no experience with the others on that list.