Good morning J, I am not Kate - she is no longer on Mayo Connect, but let me try to answer your questions...

First, I can see that you are fairly new to the group, and that perhaps you watched the NTM videos from MUSC, it that correct?

We each go through a period, early in our MAC journey, when we think we must do every single thing suggested to avoid the germs, and it feels overwhelming! Eventually we settle into a routine that works for us and allows us to continue to live our lives.

Here is a recent discussion where you might get some answers to your questions:
https://connect.mayoclinic.org/discussion/remodeling-and-shower-heads/
To chat with others who are concerned with water safety, you can read here:
https://connect.mayoclinic.org/discussion/have-you-had-your-water-tested/
One more tip to get replies - look at the date a post was made, the respond to a recent one using the "REPLY" button.
I hope this helps get the information you are looking for.
Sue