I've used a Cascade Design "Duluth Pack" since I lived in Duluth (just a coincidence) decades ago. I don't think I spent this much, but if I did, it has been worth it. It has put up with tons of abuse. Right now, all of my bedding (thermarest, comforter, etc.) are stored in it during the day.
https://www.seallinegear.com/boundary-pack-10
I use it since I had it already. I don't really use the back pack straps that much anymore, so I'm not sure I'd pay extra for that now. A simple sling would be sufficient.
I just bought some more dry bags because most of the ones I had were custom shaped to fit into kayaks. I bought light weight and heavy weight depending on usage. Heavy weight:
https://www.amazon.com/gp/product/B00VA ... UTF8&psc=1
Light weight:
https://www.amazon.com/Sea-Summit-Light ... th=1&psc=1
The ones with windows are interesting, though probably not as durable. I have to put little tags on mine to remember what's in them (towels, socks, etc.
https://www.amazon.com/KastKing-Waterpr ... +bag&psc=1
I'm not endorsing these particular ones. When I shopped, I found prices are all over the place because the sizes are hard to determine. Read the descriptions carefully.
Based on my kayaking experience, I tend to have my dry bags secured to the boat with carbiners. Even if tucked away somewhere aboard, should I be in a "sinking" situation, a dry bag that is secured to the boat provides a huge amount of floatation. I suppose it could also be disconnected and used for flotation. The pack that you showed would be like having two additional life jackets.
Mark