Before a reader parses a single word, they have already formed an impression of the writing. That impression comes from the shapes of the letters: how wide they are, how much air sits between them, how sharp the terminals feel.
Voice, not mood
The usual advice is to pick a typeface that matches the mood of the content. That is too soft. A typeface makes a claim about who is speaking and how sure they are. A tight grotesque sounds like an institution. A humanist serif sounds like a person who has thought about this for a while.
Two is usually enough
One face for reading, one for structure. If a third is needed, it is often a sign that the hierarchy itself is unresolved, and no amount of type will fix a structural problem.
Set the body text first, at the size people will actually read it, and let everything else answer to that.
