Adoption studies indicate that differences in parenting styles have mostly small impacts on long term life outcomes of children, such as happiness, income, intelligence, health, etc..

What exactly is "parenting style" understood to mean here? I have a feeling it's something seriously counterintuitive, as many of the findings cited, e.g. parenting having "a small effect on adult drinking, smoking and drug problems" diverge radically from every other source on the subject I've ever seen. The top results of my ten-second Googling were far more in line with what I've seen before - that the children of smokers are twice as likely to smoke as their peers, which is hardly a "small effect." Given all these things, the claim that parenting has no effect on "overall health" etc. seems very, very dubious, which casts an unfavorable light on the whole set of claims. Or maybe these findings are simply specific to adopting families and shouldn't be generalized beyond that.