Ion,
I purchased an Osprey's Aether 60 (Mens size large) over the internet and found it perfect in every respect! The quality is very good; it was durable, well fitting and comfortable and also adequate for carrying everything including the extra water, food and odd botttle of wine that I bought from time to time along the way. As a point of reference, I am 6'2", weighed 180 lbs. at the beginning of the Camino, dropping to about 165 by the end. Maybe I didn't carrry enough food after all
You might end up paying a fortune in restocking fees and return postage under your method of ordering so many backpacks just for the sake of trying to determine a preference. There are all kinds of websites that review various features and make comparisons for you. Proper fit and structure of the pack is key as the pack will become part of you as you walk.
https://www.gearhunder.com/backpack-with-charger/
Buen Camino!