I have upgraded several clients to 2016R2 (Professional, Express and Essential) and they now have issues with live viewing in the Smart client. The video is displayed delayed in the Smart client somwhere between a few to more than 10 seconds
A known issue, most often caused by the the Client PC not supporting Hardware acceleration. Search the Community for this term. Also, you may want to try the Smart Client options regarding buffering for each Camera Property.
Further, the Smart Client Options → Advanced → Maximum Decoding Threads may impact the behavior. Try the Auto, Normal and the number of cores of your CPU
If all else fail, you can run with the Smart Client 2014, and retry later with the Smart Client 2016 R3, which is to be released quite soon.