See some answers in this post: https://www.researchgate.net/post/RMSE_or_NRMSE_Which_is_better_to_assess_numerical_model_performance_evaluation_and_why
The numerical results of any mathematical model can be evaluated by comparing them with related experimental data using statistical tools such as RMSE, RSS, R, R2, and others
sometimes the use of some statistical tools such as R2 does not give a clear analysis of the results, so we have to use additional tools and this topic can not be predicted until after obtaining the results and analyzing them.
Really, one can not emphasis what the criterion can use to sure from convergence in generally. But from its problem may usually draw out suitable criterion.