If you're on Windows 10, the built in games recorder is pretty fantastic, I prefer it over Shadowplay. Of course, a lot of people trying to avoid telemetry are probably still avoiding Windows 10.
It's replay buffer where you start the replay buffer and it will keep the last n seconds of footage in a buffer. You set a keybind to save that buffer to file.
There are some older versions of nvidea experience floating around that still work with shadowplay without the login.