Regarding the Nevada crossing specifically- I managed fine with a 3 liter Camelback and 2 full water bottles each day during those several long days crossing Nevada with 80-100 miles of riding and no place to refill during the day. I brought water purifying tablets for emergency use but frankly I don't remember seeing any running water crossing Nevada. The days in this section are long with an average 3 summits per day but the climbing is generally easy in the 3-4% grade range.
I travelled CC style so can't speak to camping but if you do camp you will want to start your day with a full load of water and not sure you will find any unless in a town.
Good strategy is to try and avoid the afternoon heat, wind and thunderstorms. Get an early start...before sunrise...and you will finish your day by early afternoon.
The Nevada section of the cross country ride was my favorite due to it's remote and solitary nature and it felt like a "real" adventure. I look forward to doing ti again one day.