Louis B. -
I've ridden the Western Express across Utah & Nevada three times
and much more remote US 6 twice. (168-miles section with ero services)
The Western Express is nothing to sneeze at.
Granted, you will have ridden more than halfway across the U.S. by then,
but that's another issue - the heat of late summer.
I strongly suggest that the Western Express be saved for a later tour.
Would you die and your parched bones be found 50 years later? Probably not.
But you might find the touring exhausting ranging towards miserable.
On the TransAm you are rarely more than 40 miles from services,
plus, the TA has far more bicycle-oriented services - camping, bike shops, etc.
The Western Express has 70-80 empty stretches in Nevada & Utah -
And the biggie between Hanksville and Blanding - 125 miles.
I believe that the Hite Marina is long-closed du to low water levels.
There is water avaiable at Natural Bridges - which still leaves 95 miles to Hanksville.
August Temperatures -
Hanksville, UT Hi 95 / Lo 58
Milford, UT Hi 90 / Lo 54
Eureka, NV Hi 86 / Lo 53
Wisdom, MT Hi 78 / Lo 35
Kooskia, ID Hi 87 / Lo 53
John Day, OR Hi 88 / Lo 48
It is only slightly cooler, on average, on the TransAm -
but you have more shade in the form of forests and places to stop.
Nevada Highway 722