Peak Design Travel Backpack 2-in-1 Review
"Two Bags, One System"
The only bag covered here that has an integrated zip-on day bag built into the bag. Large capacity on the travel bag, perfect box for packing. Excellent straps. And the day bag is damn good for a little rambler.
Similar Highly Rated Products:

Pakt Cero Travel Backpack
Light + SleekIncredibly lightweight and durable. A personal fav for sleek minimal travel when I don't want to check anything in or struggle with heavy carry.

Pakt One Travel Backpack
Modern ClassicAfter the success of their killer duffel bag, Pakt partnered with Chase Reeves to design a modern travel backpack for both pro travelers and weekend warriors alike.

Pakt One Travel Duffel (28L + 35L)
Dual SidedThe Pakt One travel bag is a stylish and extremely well thought through duffel bag for conscientious travelers. I definitely miss the aesthetics of V1 of the bag, but the dual sided usability of this thing is killer.

Tortuga Pro Backpack 40L
Padded. Protected. Burly.Durable sailcloth, super comfortable straps and back panel, maximum carry-on size. Available in 40L and 30L versions.

Nomatic 40L Travel Bag
Weatherproof. Boxy.The Travel Bag from Nomatic is a solid offering in one bag travel both as a travel backpack AND a duffel.

Bellroy Venture Ready Duffel (40L)
Simple & ElegantSimple, large opening, excellent materials. An instant favorite for the simple, solid duffel along with the Peak.