You run 2 different Settings
first:
23:58:22: Video Encoding: x264
23:58:22: fps: 60
23:58:22: width: 1920, height: 1080
23:58:22: preset: slow
23:58:22: profile: main
23:58:22: keyint: 180
23:58:22: CBR: no
23:58:22: CFR: yes
23:58:22: max bitrate: 3000
23:58:22: buffer size: 3000
23:58:22: quality: 10
which is absolutely impossible to run even on a streaming only machine with an i7 4790 and especially when used as gaming/streaming machine. On top of that streaming 1080p60 is not recommended in anything other than League of Legends/Hearthstone and some other lightweight Titles.
If you want 60 FPS downscale by 1.5 (1280x720) if you want 1080p stream with 30 fps
And simply leave the Preset on Veryfast the gains for a slower Preset are marginal though the loss with faster Presets are simply to extreme if its not for Local Recording.
Also check CBR.
Btw on Games like Overwatch quite a few Systems have Issues even streaming 720p60 though its getting better with time and Game optimization.