Big Sandy in the Winds is not far off trail, and much easier as a resupply than the hike and long hitch to Pinedale. One huge difference between the Winds and the Sierras is numbers of people. You may well see 50-100 people a day in August, plus horses and llamas. It's a beautiful place, but much more populated than you would expect.
The desert section from Atlantic City to Rawlins is usually only 5 days. It's relatively flat, and though the sand can slow you down, it is easy to do bigger miles there. Not absolutely necessary, but doable.
Chief Joseph/Lost Pass to Leadore is a long carry. There is a lot of up and down on the Divide there.