you are much better off using a proper backpack and putting your camera gear in it. or strap a small camera back to your backpack. you will not have a good time trying to pack weight in a camera bag. i just put my lenses in their soft cases in the lid of my gregory pack, and hang my camera in a dry-sack (brooks bag) off a shoulder strap, or on a capture clip if its dry out.
you arent going to get a hiking backpack on as carryon
Get a real pack... a true backpacking pack.... No camera gear pack will ever be half as comfortable. If you start hanging sleeping bags, tents, sleeping pads off of your camera backpack you are introducing yourself into a walking hell.... the stuff will be unbalanced and will sway with every step. You will tire yourself out fighting with your load.
Get a monopod that you can use as a hiking pole... you will appreciate it for balance and it saves the knees when going down steep grades / rockhopping.....
Look at lightweight camping gear and leave all the crap gadgets at home... An awful lot of what people carry is useless... you would not believe the kitchen gadgets I have seen abandoned on trails All you need for cooking is a small stove (I have an MSR Whisperlite), a small pot (1.5L titanium), a plastic cup, a spoon, a pair of chopsticks, and your swiss army knife... And dehydrate your food! Makes it lighter and easier to cook and burns less fuel... Get a lightweight tent/thermarest/down bag and 1 spare change of quick dry clothes and you are ready to go. If your pack weighs 10 kilos (before camera gear), you have too much stuff.
My favourite pack is still my Coastal Mountains backpack, still going strong after 25 years of use, a Lowepro holster bag for the camera/lens, and a betashell for the second lens.