The science around what fats are good or bad is so confusing I don't think we can say much about them with certainly, except that trans fats are probably bad. I lean towards "eat whole foods", but those can include anything from beef and coconut which are full of saturated fats, to fish and nuts which are full of polyunsaturated fats.

I think that depends on the individual, or maybe on the dose. Years ago I read a bunch of books arguing for saturated fat, started eating a lot of it, and my cholesterol and triglycerides got horrifically bad. Even those books, which claimed high cholesterol is no big deal, were like "but if it goes over X then you need to fix that," and I was over X. I had high particle numbers too, which the books agreed was pretty bad. I went back to my normal diet and that took me back to my normal bloodwork.

Citation Needed.

My understanding is that the very few studies that showed positive impact of "adding" saturated fat turned out to be a replacement issue. They replaced junk (candy, refined carbs) with sat fat. Replacing with MUFA and PUFA showed a much greater effect.