I haven’t used the First Ascent packs but have used the Cape Storm overland, which as far as I can see is a pretty similar setup in terms of the frame and straps as the FA. As far as I know KWay/FA/Cape Storm are all the same company, so assume using the same manufacturer for everything.
My experience has not been great. In trying to avoid making pack sizes it means nothing is fixed and rigid, everything is adjustable which felt like it resulted in constant fiddling to try dialing it in which never quite got there. Also can’t say all of the looseness in the system gave me a lot of confidence in the load transfer.
At the price of the Jupiter I would definately suggest looking at Osprey or Gregory. Well made and tested, variable sizes, proper reviews available to you and they both have amazing warranties. If you can make do without hipbelt pockets, or hack a solution, the Osprey Exos 58 is a great carry and pretty versatile. Haven’t used it personally but the Gregory Optic seems to be their equivalent.
Dropping a KG off your pack weight vs the Jupiter also holds a lot of appeal!
Naturehike has an interesting looking 60L pack at the moment, appeals to me in terms of stripping off most of the junk. But fixed size so not sure I would be that keen without being able to try it on, and not sure about the longterm suitability of the front netting in our thorny environment.