Choosing a tourist backpack

Volume. The larger the volume, the greater the weight of the loaded backpack will be. Calculate your strength: the universal volume for women is 60 liters, for men - 70 liters. Try not to buy extra-small models, so that later you do not attach some of the equipment to the outer surface of the backpack. And too large displacement and empty space in your backpack will gladly take advantage of satellites that have “nothing to fit”.

Back. If you are planning long routes, carry loads weighing 18 kg or more, choose an anatomical back. For small outings in the summer, when there are few things and comfort is important, you can choose a model with a mesh on the back. Touring models come with adjustable and preset backrests. The first option is more convenient, but a little heavier and more expensive. The second option must be carefully measured, by analogy with clothes.  https://scinotech.com/beach-bag-types/
Weight. Reducing the weight of your hiking gear starts with the backpack itself.

Additional features. Conveniences with which some models are equipped. This can be an additional side entrance to the backpack, or compression straps. Or built-in rain cover.

Valve. Large volume backpacks do not end with a zipper, but with a flap. It increases the volume of the backpack. A rope or other bulky item can be attached under the valve. It is recommended to buy an adjustable flap that can be removed from your backpack and used as a small purse or organizer.

Drinking system. Most backpacks are equipped with a drinking system. But if this is a critical point for your journey, choose a model with a well thought-out design for your drinking system: a tank and a pipe.

Waterproofness. Check before buying if the backpack will get wet from the fabric of your choice.