Yes the loudness and frequency can be changed but that it.
When I say frequency, it’s just Low, Mid or High to choose from.
Can’t remember off hand but I think the audiologist can set the Mics off for music but definitely not for phone calls; as you say, it’s because they need to be live to pick up your voice.
Lower for music? As I said earlier, the max is -10 dB for Mic.