For inpiron 15 7000, you have to play 1080p and let the GPU upscale to the 4k panel. It will not be as sharp but still playable at good frame rates and mid-high graphics options. The level is same or slightly better than PS4 gaming. Otherwise you can output HDMI to TV to play at native 1080p.
And other otherwise, there is alienware line, with 970m or 980m, and the same aggressive gamer motif like RoG or MSI or Aftershock, but when you bring in Dell pro-support, you can feel safer Dell will insta-service the heat abused gaming laptop better than the rest of them.