Well, in fact, there are some configurations that only the plugin owner can do.
For example, if you’re using some authentication scheme, you will have to add some additional verification tokens to your manifest and provide some client/secret ids to ChatGPT.
So, when you use the “Develop your own plugin” flow, ChatGPT is going to provide the whole wizard to configure your plugin and these tokens for instance.
Once it’s configured, any other developers (including you) can use the “Install unverified plugin” to fetch the same manifest file. However, they will not be asked for any additional configuration since you did it already.
That’s the difference I understood. Hope it helps 