Thanks guys, reinstalled the 970 and was able to reproduce the same problem. Checked with folks using this software and it's definitely a bug. For some reason, when working on a 4k display and you don't scale the screen so text and UI graphics are enlarged for easier reading, the rendering rate in my case increases by a factor of 3 or more. Complex and fast moving scenes can sometimes come out distorted like that. But sometimes it works out great with no noticeable degradation in quality. Running a test as I type this message on a pretty hairy scene.
Started using this and Cinema 4D with vRay to do storyboards explaining virtually on how new engineering concepts work for my job. My boss really likes the realism of vRay with C4D, but it's such a pain to setup everything. iClone was supposed to release an iRay plug to improve quality this month but delayed it until Q1 of 2019