Is taking some of Sheikh Ibn 'Uthaymeen's fatwas and leaving others, such as the issue of the niqab and women wearing trousers, considered zandaqa (heresy/apostasy) or following one's whims?

When jurists differ on the ruling of an issue, a Muslim should be cautious and scrupulous, and keen to know the preponderant opinion, seeking assistance from Allah Almighty and supplicating for guidance to the truth in what has been differed upon. A supplication from the Prophet, peace and blessings be upon him, recited at the opening of the night vigil (Qiyam al-Layl) indicates this. And know that adopting a less weighty opinion does not lead its proponent to the degree of apostasy (zandaqa); rather, he may be disobedient if the preponderance of the differing opinion becomes clear to him.