FNetworkPredictionDriver is how calls to the driver are made. FNetworkPredictionDriverBase is a default implementation that will be used. You can customize any of these calls by specializing FNetworkPredictionDriver to your ModelDef type. If you do this, you should inherit from FNetworkPredictionDriverBase or FNetworkPredictionDriver if you are extending an existing ModelDef. (otherwise you will need to implement every required function yourself).