Rivatuner lets you see all your stats and temperatures at once.
http://www.guru3d.com/content-page/rivatuner.html
It's a bit hard to set up, though.
Then there's Open Hardware Monitor
http://openhardwaremonitor.org/
It displays the temperature and usage of your computer in percentages. (But not in game.)
That set up will be more than enough to play Witcher 3 at 60fps on 1080p.
However, if you move to 4k resolutions it may lower in frame rate just a bit.
You could also try FRAPS to monitoring your framerate and recording video.
or Nvidia's Shadowplay...