Buy the Adventure Cycling map
, which answers all these questions. Without undercutting the income that supports all the good things they do, I can summarize a bit. The valleys are rolling terrain with many local roads. Going over the mountains between the valleys, you will share the few available roads with cars and trucks. These are steep and many have little shoulder and short sight lines. The profiles show you what to expect for number, length, and slope of climbs. The Riding Conditions section discusses the traffic and roads, including a few tempting shortcuts that you would be sorry if you tried.
Parts of the route are unpaved. Conditions vary with recent rains, when the grader last went through, and how much dust rises in dry weather. No one can predict this for you.
I have ridden only a few parts of this route, and can say I found it beautiful and challenging. Others with more experience will soon chime in, I hope.