Get Plugin Child Plugins architecture

I don’t think there is any specific “correct” method of organizing your plugin modules. If you want to be listed in the official repository, your plugin cannot contain any crippled code, the free version must be completely functional. You can up sell other modules available through other resources.

Actions and filters are certainly one way for children to interface with their parent, but other techniques are possible as well. The best one will be dictated by what your plugins actually do. Some functions that may be useful include is_plugin_active(); function_exists(); class_exists(); etc. As long as what you do is well organized and clear, I expect it will be fine.