AER Go Pack vs Millican Smith Roll 18L Pack

These are going to be more suitable for ‘true’ one bagging (ie when you travel without a checked bag). If you decide to opt against a checked bag, perhaps look at a packable day bag and one of your options above, or take a look at the Peak Design Travel Bag, as this is designed with photographers in mind, is effectively a big bucket of a bag, and can expand from 35-45l (although I think when expanded to the full 45l it is slightly too big for most airlines). For a daily carry, you ideally want to be looking at something 25l or less, even under 20l.

You've got another one on this side. You've got this large roll top pocket here that will expand out. As you can see, quite large, really a big bag, b...