Packing for one bag travel can be a challenge, but not impossible.
If you're new to one bag travel and plan to take trips of a week or more, the Outbreaker and Setout Backpack are right for you. They're a maximum-sized carry ons for city travelers with ample packing space for a week or a month of travel.
Seasoned onebaggers should consider the Setout Divide Backpack, which is a more compact option with an expansion zipper for more flexibility.