In theory, at least, you could build a cellphone around a GPU with a couple ARM cores thrown in and keep most of the GPU powered down while you are not docked. When you are connected to a decent power supply over USB-C, you could fire up those cores, provided your phone's back is a massive heat sink (a dock can provide the airflow).
It won't beat a 300W monster or accurately predict the future weather for 10 years, but it'd be more than reasonable for casual gaming.
It won't beat a 300W monster or accurately predict the future weather for 10 years, but it'd be more than reasonable for casual gaming.