The media foundation VCE encoder has some issues. That's why we're trying to deprecate the media foundation encoders like we recently did with NVENC and QuickSync, we implemented proper versions of those encoders because media foundation encoding was terrible. So unfortunately I wouldn't really recommend using it, I feel like you could encode with x264 on that CPU without impacting your games anyway, especially at 720p like you have it set to. Your CPU is one of the better ones out there, it can handle 720p with x264 just fine while gaming I feel.