Just set up an Arc and the volume varies greatly between apps. I (and my bird/dogs/partner) are often blasted when moving from one app to another.
ex: Watching a movie on Netflix and then move to a Youtube video and the sound jumps up 2x. I lower the volume to a reasonable volume then move to something else in a different app and all of a sudden the volume is loud again.
I haven’t tested thoroughly, so I’m not sure if it indicates a consistent ratio/difference between apps along some linear spectrum, or if the difference is consistent across specific apps.