A user of Windows observed, that the new build breaks Windowed G-Sync following the installation of driver 381.65 and running it with both AU and CU (with DDU after installing CU).
Initially, there was a good performance during benchmarks but later some issue was experienced with G-Sync and CU. To be precise, Windowed G-Sync seems to be broken. Moreover, while playing a game on Windowed/Borderless Windowed, stuttering and FPS jumped from 50-100 in no time. This was not to be seen with the same driver version with AU before I updated and the problem was solved once back to Fullscreen.
A Reddit user who faced this problem has also posted how he fixed the problem. Perhaps it will help you if you too are facing this issue.http://news.thewindowsclub.com/creators-update-breaks-windowed-g-sync-here-is-the-fix-89392/