Is a young man whose mother becomes angry with him because of his commitment to supererogatory acts of worship (nawafil) and permissible matters (mubahat), and his wearing clothes she dislikes in order to please her, considered disobedient to his parents (aqq)? And can Allah punish him for that?

The mother's right is immense, and obeying her is obligatory in matters that benefit her and do not harm her child. If she commands leaving a recommended act, obeying her becomes obligatory if she has a valid reason. If you exert your utmost effort to please her, be dutiful to her, and obey her in what is right, then you are not disobedient, and her subsequent displeasure will not harm you. We advise you to continue being dutiful to her, showing kindness to her, and obeying her in what is right as long as it does not harm you. There is no blame in informing her of what is difficult for you.