I'm not sure how powerful the 960m is considering its a mobile gpu, nvenc should have very little performance impact but it could be that you are pulling just around 60 fps before streaming and then after you might be having dips below. How choppy does the game get, and is the choppyness the same across all games, is it worse in some while better in others? If so that could point to a lack of power to run the games while doing something else like streaming/recording.
In any case here are a few things you could try in the meantime, before you do any of these things please turn on the in game FPS counter in steam by going to the settings of steam. That way you can measure the impact of each thing you try, if they get better then you're in the right direction. Do a baseline reading first to see your performance (not streaming and streaming) and how it is affected by your current setup.
1. Try using x264/quicksync (if your processor supports it) and see if the problem persists. x264 will more than likely have more of a performance impact on the games but its still worth a shot to help dissect the problem. Quicksync if applicable will perform similarly to nvenc in terms of preserving the performance but will have slightly less quality than nvenc.
2. Make sure that you are using Game Capture and if that is unable to work use window capture.
3. Try to record/stream your file/temp file to a different hard drive than you are playing on, not sure if it could affect performance of a game but its likely especially if your playing off a hard drive, the slower the drive the worse this could be. This might especially be problematic if you are running OBS, recording/streaming the file/temp file, and playing the game all on the same hard drive. I can't imagine that being easy for a mechanical drive (or possibly even an ssd) to keep up with all of those things happening at once.
4. I'm not sure if OBS would consider the Intel HD graphics as a GPU, so just try setting the "GPU" number in nvenc to 2, if that doesn't work try 1, if neither work just put 0. The reason I mention to do this is because in the log it pops up as the display adapter 2. So maybe changing it to 2 will help with that if the default one isn't reading properly. This probably won't work but its worth a shot to see if anything changes.
5. Once again under the nvenc codec uncheck "use 2 pass encoding" if applicable, see if that helps as that is slightly more intensive on your hardware.
6. If this problem wasn't always happening try uninstalling OBS and doing a fresh install of it.
Sorry for getting back to you so late, hopefully one of these things works! +)
