Follow the below changes and then uninstall v1.x so that it's easy to migrate without any compilation errors. Else you can simply uninstall and go with the below changes. Both ways are fine.
Version 2.0 changed the root namespace of the plugin from
VoxelBusters.NativePlugins to VoxelBusters.EssentialKit.
Version 2.0 dropped NPBinding interface access and now you can directly use the feature name.
V1 used to have all of its settings in the NPSettings asset object. Now this got renamed to Essential Kit Settings and is moved to Assets/Plugins/VoxelBusters/EssentialKit/Resources folder.
Version 2.0 follows a standard format for callbacks with a Result and Error objects
public delegate void EventCallback<TResult>(TResult result, Error error);
In the above, result is the data for the operation and Error object is a wrapper for error details.
public static void LoadLeaderboards(EventCallback<GameServicesLoadLeaderboardsResult> callback)
EventCallback result contains GameServicesLeaderboardResult value an error object if any error occurs while loading the leaderboards.
If you have any custom images (for ex: Large Icon image used for notifications), move it to Assets/StreamingAssets folder.
Folder structure of the plugin got changed a lot from v1 and its more cleaner now. All the plugin files will be in Assets/Plugins/VoxelBusters/EssentialKit now compared to earlier version where it was too much distributed.