Hi and Low Pass Filters to reach ACX -60dB level

it is weird that the noises only show up once you start narrating.

That’s a significant symptom. That can be Windows Services trying to “clean up” your voice for chat or conferencing. Gating can be one of the tools (ACX doesn’t like that very much).

Dig into Windows settings and make sure all the enhancements are turned off.

Koz