> Also for whatever reason, the lerping functions don't seems to work properly, they just wait and then instantly update at the end.
Did you enter 1 into the granularity field. The WebGL build isn't completely self explanatory, because it is more meant as a tool programming wise. But the granularity is how many steps it will take to decrease to the given endValue in the given time frame. Meaning if you enter 1 it doesn't actually lerp. This might be what happened, because at least for me the Lerp works like expected.
> Playing a clip when another is done. (nice because many songs have an intro that plays once, and then a looping part)
The AudioManager WebBuild sadly does not show all the possible features because some features aren't that easy to display via. a simple UI interface, but there is a method that allows to subscribe a callback at any point in the songs time, meaning you can easily just subscribe to the end of the sound and then start playing the next one.
> StopAll/PauseAll/FadeOutAll functions that can be called when pausing the game
This should also be possible, because the tool has integrated support for AudioMixer API, meaning if you enter the outputAudioMixerGroup on the AudioSource, you can change multiple sounds at once --> There is even a lerp version that allows you to change an exposed Parameter on the AudioMixer for all AudioSources that use it.
If you ever want to have a look at it or use the tool theres a github page with detailed documentation on the features. https://mathewhdyt.github.io/Unity-Audio-Manager/
For all the other features, will definitely take note of it thanks for the feedback definitely highly appreciated and I'll see what I can integrate :D.