The Mira may well be discontinued so only remaining stock listed.
I have the 34lt Mira in the grey/aquaish combo. Bought it off Gumtree ?3 years ago from someone who had bought it to walk a Camino that they never did. The hydration bladder lasted awesomely and I used it on all my trips skince purchase. Sadly I lost some parts to it so that is the only reason it is retired. The pack itself still looks brand new- embarassingly so

It is like I just bought it from a store to go walking with. I have flogged it yet it looks great. It is supremely comfortable, but I will say, over engineered for a day pack with the AG harness it has. I do appreciate the harness system when fully loaded out, but most trips it is not really necessary. I did own an Aura for a few years too until I got too small for it. I was happy with it. My kids have a Renn and a smaller older kids pack from Osprey too purchased 2nd hand from a forum member. Even my daughters school bag is a pay it forward Osprey day pack from a fellow forum member, so have used the brand a lot
I understand the issues with trying things on when you don't live close to a store. I have the same issue so tend to go through some gear in the quest to get things right.
If you can look at some other brands, you may well find some packs that suit you better than the Ospreys. Having said that, I have been really impressed over the years with the quality and the customer service too, which I did have to use when I overstuffed my backpack and broke a zip. They do stand by their lifetime warranty.