did a benchmark test for you
no game running Usage
6% CPU
59% ram
0-3% GPU
Game running idle aka idling the start menu Usage
31% CPU
69% Ram
100% GPU
Game not running idle aka playing the game Usage
60% CPU
69% Ram
41-51% GPU
50% Heat is CPU being over used
25% Heat is GPU being under used
5% Heat is Ram being very under used.
Just a Note last time, I seen a game run 100% GPU on game start menu the start menu was still being loaded when in game, so its possible that the start menu is still loaded when playing the game, and not unloaded.