Specific conditions on the Dalton (and other dirt/gravel highways in the region) are rather dependent on the weather and on where they happen to be doing construction. When I took the Dalton all the way to Deadhorse and back on my Alaska trip a couple years ago, it was definitely doable but not a gentle ride, partly because it's something like a thousand miles of variably rough road. For the most part it was fairly decently smooth gravel roadway, or gravel roadway in various stages of being reconstructed to be fairly decent.
I saw only a few travel trailers, genearlly smaller ones, and more truck campers or SUVs with rooftop tents. I think I may have seen at most one or two other class C's, generally smaller ones. I definitely felt in the minority going in a 32' long motorhome. I don't recall seeing any fifth wheel trailers, though there may have been one or two. I am very glad I went, but it was hard on the motorhome; I'm not sure I would take my RV over it a second time. It also got very, very dirty, to the point where it was impossible to tell that there were stripes and swoops on the sides.
As for road conditions, enquire locally; one good place would be the Morris Thompson Cultural and Visitors Center in Fairbanks (which is well worth visiting in its own right).
