Hello @szfpro, thank you for your post. Version 2 audio unit plug-ins are bundles with a .component
extension that the host process, Logic Pro in this case, can dynamically load. Audio unit .component
bundles are usually installed in the /Library/Audio/Plug-Ins/Components
or the ~/Library/Audio/Plug-Ins/Components
folder, but a host app can load them from anywhere in the system. Loading always happens in-process.
Version 3 audio units, on the other hand, are app extensions. They are .appex
bundles bundled within a container app and made available to the system from there, so there's no need to install them. You distribute an audio unit extension by simply distributing its container app.
Host apps, including the container app, can load audio unit extensions with instantiate(with:options:completionHandler:). Loading usually happens out-of-process, that is, the host and the audio unit communicate via XPC. On macOS you can structure an audio unit extension such that the host can optionally load it in-place. The Creating Custom Audio Effects illustrates how to do that. Still, the .appex
bundle will live within the container app's bundle.