What to do with CFBundleIconName and Asset Catalog

Question

There are various tutorials (like here and there) that explain how to add alternate app icons to an iOS app.

The addition to the MyApp.plist includes a CFBundlePrimaryIcon item. That gives me the impression this will now be used as the default icon and replaces the old/previous way of setting a single app icon using CFBundleIconName MyApp.plist entry and the Asset Catalog App Icon Set Name Xcode target build setting.

However, none of the tutorials even mentions the CFBundleIconName MyApp.plist entry nor the Asset Catalog App Icon Set Name Xcode target build setting.

Neither is discussed what to do with an AppIcon image set in the asset catalog. It's also not explained why the alternate app icons (which includes the CFBundlePrimaryIcon) are not placed in the asset catalog, but as separate files instead.

And, I have a few other questions; I don't like following magic tutorials (that have slight differences) without understanding/knowing all details.

Does anyone know where Apple documents all the details? I only found a few lines here and there that state you can now have alternate icons and which top-level .plist key to use.