Dell Inspiron 15 Gaming (7567) + external monitor = (performance) problems
Although the notebook seems to be powerful enough, I am having problems when it is connected to the external monitor (via HDMI, I have tried different monitors and cables):
1) When the notebook lid is closed (or the Windows Display settings is set to "External only"), Windows is very slow, all the animations are lagging. When both notebook screen and external monitor are on (set to "Duplicate"), everything is fine.
2) In games, I have a noticable FPS drop (up to 20 - 30 FPS in Witcher 3) when playing on external screen (even on "Duplicate" and "External Only" modes). I can have full FPS just when playing only on notebook screen.