Duffel & soft luggage
1000D waterproof cordura racksack system with fully harness-mounted tool and hydration options.

Verdict
Soft luggage done properly: harness-mounted, genuinely waterproof, and it survives being dropped on gravel.
The OS-32 pair mounts on a harness rather than bungees, so nothing shifts when the surface turns to washboard. Three long trips in, the straps show no fraying.
Everything inside is dry after a river crossing that submerged the lower half of the bags. That is the whole test.
64 litres is enough for three weeks of camping if you pack to a weight budget. The modular add-ons (tool roll, hydration sleeve) attach without extra brackets.
It is not lockable, and the fabric collects dust in a way hard panniers do not. Neither has mattered in practice.
Packing light for three weeks
The field guide behind this review.