The current default is that it will do a full sync on the background every couple of minutes.
We're still in beta stage of development. Because we use the native Kodi database with this new approach the above limitations are gone! You can browse your media full speed and all other Kodi addons will be able to 'see' your media. The new Emby addon synchronizes your media on your Emby server to the native Kodi database. Especially on slower devices this can take too much time. With the old MediaBrowser addon for Kodi we have a couple of issues because you browse your media as a 'video addon':
The Emby addon for Kodi combines the best of Kodi - ultra smooth navigation, beautiful UIs and playback of any file under the sun, and Emby - the most powerful fully open source multi-client media metadata indexer and server.
A whole new way to manage and view your media library.