I've been on a few western hunts for elk, mulies, etc. I used to carry a backpack but now that I'm older I now use one of Bass Pro's Extreme fanny pack. This pack is plenty big enough for extra socks, rain gear snacks.and a lot more other stuff you wish to pack. It has shoulder straps that take the weight off you hips and has a padded belt which is removable. It also has 4 buddy locks to add any accessory pouches (water bottle, rangefinder case, etc. )
I leave the guide carry the spotting scope.
Everyone has their own opinion, so I guess I'm throwing mine in. Its what works for me.