Everyone has an opinion so this is just mine, and nothing more, but I have a strong one about dogpacks and dislike the Ruffwear and similar ones. The reason is that they are made for the buyer and not for the dog. Heavy, over engineered but badly fitting.
Look at how you choose your own backpack, or a pack for your child. The old ones that hang like a sack in the small of your back work but they are not comfortable when getting heavy. Add uncomfortable fit and chafing and they are not good at all.
A modern backpack which fits your body and size, distributes the weight on your shoulders and in it self weighs very little is what you would choose for your self. Now look at the dogpack. It should put the weight on the shoulders of the dog, as far forward as possible and not on the lower back. It must fit, not hinder movement of the dogs legs or shoulders and
must not chafe! A good pack has straps that lifts the bags out from the sides and distributes the weight onto the back. Also the pack must be strong and durable but not heavier than necessary when empty. The ones I like best are often made in norway as they have spent many years perfecting their designs. They are often even more expensive but at least you get a good product that will last several dog lives.
Not a good picture but the only one I have at the moment. These are made by "Nordtro".