There are some universal truths here:
1. If it is good to drink, it is good to brew.
2. Duplicating classic styles requires water similar to the original source .
3. Any amount of chlorine, chloramine, iron or magnesium is always too much but not always so much to not be tolerated.
4. Homebrewers don't need to follow anyone's rules.
5. At least some mineral content is needed for all grain, distilled water is acceptable with extract.
6. Understanding water science is an important consideration if you intend to produce a specific beer but is also not all that important if you just
want to make good beer.
7. Water chemistry for brewing is an advanced topic that only gets more complex the more you learn.