Keep in mind that MediaImport is more than just getting Emby content into Kodi. it predates Emby for Kodi.
With regards to offline devices and startup sync, it will be more less the same as Emby for Kodi. And yes it would depend on server plugin. I think you understand that the server plugin is saving server events, hence any Emby client that is not relying on a dynamic link to Emby libraries will probably need that plugin. Once the server start storing this info, the plugin would no longer be needed.
In addition, as he encounters shortcomings in Kodi as it applies to imported items, he is adding features to Kodi's core to enable it to handle it more efficiently and elegantly. This will also be to the benefit of Emby for Kodi and EmbyCon. In some cases they already have. So a win win situation.
In response to a similar question, I wrote the post linked below.
Hope that helps.
If you have further questions, please ask away.
Edited by LongMan, 15 January 2020 - 10:44 AM.