I am also concerned with the following arguments. Still, I can probably clear up some of the questions for you.

From what I’ve inspected from the logs, load_best_model_at_end argument is ignored during the hyperparameter search.
Since load_best_model_at_end is ignored, I believe all the corresponding args (e.g. metric_for_best_model) are ignored as well - at least reproducing the results while changing this parameter, I get the same values.

Hope @sgugger can clarify.