What is the ruling on wrapping the headscarf in a way that shows the size of the head, and is it permissible for a woman to show the size of her head? And what is the ruling on wearing loose-fitting trousers that do not reveal the size of the legs?

There is no harm in covering the head with anything that achieves concealment, even if it leads to the head's volume being apparent. It is permissible for a woman to wear loose-fitting trousers that cover the 'awrah and do not reveal the size of the limbs, if she wears a covering garment over them, provided that it does not involve imitation of men or disbelieving women. She is prohibited from going out in front of non-mahram (definition) men in tight trousers that reveal the size of the legs, due to what is narrated in the hadith (definition) from Usama ibn Zayd (may Allah be pleased with them both), that the Prophet (peace be upon him) commanded him to tell his wife to wear a thick undergarment beneath her Coptic garment, for fear that it would reveal the size of her bones. Al-Shawkani said: "The hadith indicates that a woman must cover her body with something that does not reveal its contours." Umar (may Allah be pleased with him) forbade women from wearing Coptic garments, because even if they are not transparent, they reveal the contours. Asma bint Abi Bakr returned a garment that she was told was not transparent, saying: "But it reveals the contours." Al-Buhuti said: "It is disliked for women to wear anything that reveals softness, roughness, or size."