You have Game Mode on, read this
https://obsproject.com/wiki/How-to-disable-Windows-10-Game-Mode
You are also Skipping Frames though
02:54:49.630: Video stopped, number of skipped frames due to encoding lag: 13/574 (2.3%), you will be better served using your 970 and NVENC for encoding
...Full stop
You are rescaling your output from 720p up to 1920x1080. Do not rescale output on the Streaming tab.
02:53:55.466: video settings reset:
02:53:55.466: base resolution: 2560x1440
02:53:55.466: output resolution: 1280x720
02:53:55.466: downscale filter: Bicubic
02:53:55.466: fps: 60/1
02:53:55.466: format: NV12
02:53:55.466: YUV mode: 601/Partial
02:53:55.468: Audio monitoring device:
02:53:55.468: name: Default
02:53:55.468: id: default
02:54:39.043: [x264 encoder: 'streaming_h264'] preset: veryfast
02:54:39.044: [x264 encoder: 'streaming_h264'] settings:
02:54:39.044: rate_control: CBR
02:54:39.044: bitrate: 2500
02:54:39.044: buffer size: 2500
02:54:39.044: crf: 0
02:54:39.044: fps_num: 60
02:54:39.044: fps_den: 1
02:54:39.044: width: 1920
02:54:39.044: height: 1080
02:54:39.044: keyint: 120
