I know this is long, but I think it has all the details for someone to provide the answer.
First off, I'm using the full version of Bandicam, recording at 1080p 90q using H264 -NVENC (VBR) at 59.94fps, on a 4K, 60fps monitor (but I don't record OR play in 4K when recording. I play and record in 1080p when recording). The monitor does not have G-Sync. I have a GTX 1080TI and a 6600k OC'd to 4.5GHz. I play games on 1080p resolution, and record with the Screen Record mode in full screen in case a game ever crashes (I don't want the file to have a chance of getting corrupted, and sometimes I like to record stuff outside of the game).
I also record my Logitech Brio on auto settings (it won't detect unless I choose "auto", and even then I sometimes have to restart for Bandicam to pick it up). I record the webcam and the screen as two separate files. I import my screen recording to Premiere Pro first to get a 59.94fps timeline, then drag in my webcam which records at 30 (which Bandicam chooses to do in "auto"). I also use Bandicam to record my XLR microphone at 48000Hz, instead of the Brio's audio (Audacity would randomly stop recording sometimes, so I put the burden on Bandicam).
So, the games run flawlessly (even on 4K, but ESPECIALLY on 1080p) and when I'm in the game, there is absolutely no screen tearing while recording. I have specifically tested this while recording. If games have V-Sync, I enable it. And yet, the video file sometimes has moderate screen tearing in the bottom 20% of the video, regardless of V-Sync (which WILL remove tearing in real time, but not in the video file). If you're thinking "you must just not be seeing it", please don't think I'm blind.. if I can see it in the video, I can see it in the game, especially when I'm looking for it.
Which seems strange to me, since it's recording the screen, and there is absolutely no screen tearing on the screen when it's playing. I have recorded sample videos, with smooth movement such as camera rotation, of about 10 seconds to specifically test for this after it first happened. There is only screen tearing (again, ONLY in the video file) when the majority of the picture is changing. If a character runs across the screen with a static background, there won't be any tearing in the video. I'm also using "Use enhanced capture method", and have the priority set to "High".
I always have the latest video drivers and Windows 10 drivers. Also, the audio is AAC, 48KHz, stereo, 192kbps, with Two Sound Mixing disabled. Just in case.
Does anyone have any ideas?