I doubt if Nixon knew much of anything, other than after-action reporting.
Footnote: the assassination attempt against French President De Gaulle led to a in-depth situation where CIA figures were figured as part of that deal. De Gaulle calls Kennedy in the summer of 1963....asking what the hell was going on. Kennedy knew nothing.
“Kennedy knew nothing.”
And in the recent Trump-Tucker interview, Tucker asked Trump flat out if he thought he was made aware of everything the CIA was doing and Trump said no.
Which is unacceptable, since the CIA has no authority but what derives from the President himself. It’s obviously not enough even if the President appoints a CIA director who is loyal, because then the CIA will just not tell the director everything they are doing either. Time to tear it out by the roots and start over.