Do scholars differentiate between perpetual and non-perpetual سلس ( سلس, urinary or fecal incontinence), and do they consider intermittent سلس to be a nullifier of ablution (wudu') and necessitate taking precautions against it, and what was the opinion of the Companions regarding سلس of both types?

Intermittent impurity is not a single degree. Some Hanbalis consider intermittent impurity to be a variable intermittency, like someone who has continuous urinary incontinence. The Malikis, however, consider the impurity to be continuous if it persists for half the time or more. Whoever experiences a few drops after urinating that then stop, and can pray with purity and within the time, is considered to be like a healthy person. The jurisprudential schools, such as the Hanafis and Shafi'is, hold that a woman with abnormal uterine bleeding (mustahadah) or someone with urinary incontinence, or similar conditions, should perform ablution for each prayer time and pray, and their ablution is not invalidated as long as the impurity is continuous within the prayer time. The jurists relied on the narrations from Zayd ibn Thabit and Umar ibn al-Khattab, may Allah be pleased with them both, regarding the permissibility of prayer for someone with incontinence, and that blood from other than the private parts does not invalidate ablution. As for obsessive doubts about purity (waswasah), Ibn Abbas advised sprinkling water on the private parts when feeling wetness during prayer, in order to stop the waswasah.