I would keep on read Berger’s book as it will lay out the point that the 14th Amendment did not intend the Federal Bill of Rights to be enforced on the States (a.k.a. Incorporation)
The Ninth Amendment, in plain terms, states that the government cannot infringe on rights just because they aren’t specifically expressed in the Constitution. For example, Congress could not pass a law making it a crime to wear shoes. You could make an arguement claiming that you had that right under the Ninth Amendment (I use this example understanding fully that Congress does not have the power in general to write a law like this)
So, to answer you question more specifically, the States do not have to abide by the Ninth Amendment. States can pass legislation they see fit to govern their State, so long as it doesn’t violate anything in that particular State’s constitution. As for the ratification debates on the topic of the Ninth Amendment, I’m sure the professors can point you in the right directions on the specific documents or conversations that I don’t have easily accessible. I hope this helps.