Beginning with the NVIDIA Driver version 461.09, setting V-Sync OFF as a global setting from the NVIDIA Control Panel will likely result in tearing even when viewing content in windowed mode.
When V-Sync is enabled, the application's frame rate is synchronized with the display refresh rate in order to eliminate tearing. Typically, tearing would occur when viewing applications in full-screen mode, so V-Sync is useful in eliminating tearing in this case.
Prior to driver version 461.09, only a single plane was available to the OS. The Desktop Windows Manager (DWM) would composit the contents from all the windows and then present everything at the refresh rate cadence. This means that tearing was avoided by DWM design even without V-Sync.
However, driver version 461.09 and later supports multiplane overlay (MPO). (MPO provides benefits, such as reduced latencies, for gaming in windowed mode.) With multiplane overlay, the application is allowed to present its contents independently and with its own V-Sync setting. The OS, outside of driver control, decides which apps get promoted to their own MPO plane. If V-Sync is OFF, then there will be tearing (even in windowed mode) because, as in full-screen mode, there is now no desktop compositor controlling the presentation. Setting V-Sync OFF now has the same effect in windowed apps as it does for full-screen apps.
To avoid unexpected tearing in windowed mode, NVIDIA recommends leaving the V-Sync global setting at the default "Use the 3D application setting".