You can just turn off or blur NSFW posts in your settings. Also why when you create an account it asks you if you want to optionally enable NSFW content. That's an already solved problem. You don't need to defederate for that.
They're not particularly explicit. Most of them are just talking about sex. There was some toothbrushes that got reported for being too risque once though.
Not childporn. There's a community called "adorableporn" that originally had, as part of its description "childlike" (other descriptors were things like "cute") while being very clear that everyone on that community was 18+ (and even validating questionable posts with age verification). The wording of "childlike" has since been removed to ensure no confusion.