Whether NBC requires both parents be citizens is the more pressing issue. When one is not a citizen, it creates dual loyalties, and that is the problem that I believe the founders were trying to avoid. A President must have been born with only one allegiance. That, to me is the interpretation that makes the most sense, but it is still an open question as a legal matter, and when the SC gets its hand on the issue, if it ever does, they are likely to muck it up.
According to case law, any person born abroad (except diplomat's kids), if they are a citizen, they are a naturalized citizen. Rogers v. Bellei.
But according to on the ground reality, the law does not apply to presidential candidates or presidents.
Same principles apply to dual citizens.