Hey Jasonh2013,
For Project level Max Channel limit, you will want to go to Project Settings > Engine > Audio > Quality Levels > 0 > Max Channels (there’s an enumeration because you can add alternate Quality Level settings here)
To access the new platform settings, you will need to have 4.17. However, it’s important to keep in mind that this is a Work In Progress feature right now.
A couple of things to note that 0 on some of these parameters means USE DEFAULT and then the other thing to note is that Sample Rate on Android is not settable–since creating that field, we now query the specific Android Device’s preferred Sample Rate to avoid extraneous Sample Rate Conversion calculations.
I hope that helps you navigate the Project Settings.