You'd control that from Music settings on iPhone, not sure where or if that setting is for Apple Watch.
In the health app it will show you the decibels of headphone listeningYes, I am looking to see if the airpod pro or ios has a similar feature. I am aware that there is a "Volume Limit" in the music settings but that is not much like the noise app. You would have to decide where to limit volume.
It is a bit different using buds vs. ear over headphones.
In the health app it will show you the decibels of headphone listening