I use the 20L everyday. I got my notes, laptop and my camera. I have sufficient pockets for every pieces I need for class or photography. My only caveat is that the hip belt sit higher than where I need it and I want a bit more space. I want a 30L of the everyday zip. Please make one.
Knowing there is no perfect camera bag, I still ordered the Everyday Backpack Zip because I felt it would come close to meeting my needs. I've been using two backpacks for quite some time, one for everyday carry with computer sleeve and one for nature walks. For everyday use I have my Fujifilm X-T3 with either a Fujifilm 16-70mm lens attached and a Fujifilm 35mm f2.0 in the bag or I switch those around where the 35mm is attached and the zoom is in the bag. I also carry a A5 size journal, Kindle paperwhite, maybe a book and sometimes a 13" Macbook Pro. When headed to one of the natural areas I will bring along Fujifilm 70-300mm lens in the bottom compartment and no laptop. I do not like carrying much stuff and felt the smaller 15L bag would encourage me to carry only what I need, not what I can carry. I'm over 70 and the back is not what it used to be. So far it has worked out. I've not even consider the other two bags I used. I hesitated to order this because of the price but felt I could not evaluate the bag until I used it. Knew if it did not work for me I could return it. When I first received it I thought the laptop sleeve would be to small but it fits nicely. I find it easy to access my camera from the side or my journal from the top. So far I am very pleased with it.