Yup, bold is mostly used stylistically for headings, titles, stuff like that. (And sometimes as part of link styling, especially with a lighter link color.)

Virtually the only time it's used within text is in a textbook-type situation, where the first use of key terms is in bold, but subsequent usage isn't. Which isn't helpful/relevant if you're copying a passage from it -- just because it was the first usage in that book, doesn't mean it's the first usage in your own document.

And underlining doesn't really exist typographically except for links. It's always been the handwriting/typewriter substitute for italics. It has no established meaning whatsoever -- any non-link usage of it is idiosyncratic, which is usually not something you'd want to preserve.