I've been through it, it is mountain-type roads, but not really in the mountains. The road is crossing a series of valleys cutting a few hundred feet into a plateau, that is most of the way, less than 1000 feet above sea level. What you get are short hilly sections with a lot of curves to increase the length of the road and thus reduce the gradient. Progress can be relatively slow, with small towns and local traffic. I used the route to get around roads closed by flooding further north, did not make good time.
My usual route is US-60, which is four lane most of the way from I-57 to Springfield, and this is one that is sometimes blocked by flooding in SE Missouri, as might be 412 around Paragould. This is rare, and I don't know what is going on currently.
Depends on where you are coming from, usually best time from Memphis is I-40 to Conway, then US-65. Stays on the Delta longer, then follows the grain of the land rather than cutting across it.
Usually on trips to and from Florida or the Gulf Coast, I don't go through Memphis or Jonesboro, rather cross the Mississippi at Greenville or Vicksburg, following US-65 through the absolutely flat Delta country of SE Arkansas (and Louisiana if crossing at Vicksburg). Towns are very small and far apart, Little Rock the only metro area.
Ozark Mountains are west of US-65, north of I-40, and since the higways follow river valleys, to get into the mountains you have to be deliberate about it. The rest of eastern Arkansas and eastern Missouri is just "The Ozarks" (once you get out of Delta Country), physiographically deep valleys in a low plateau, and also a culture.
