or is it a really good OS for privacy that sacrifices in usability?

Privacy and usability are inversely correlated. Anyone who tells you otherwise either has a relatively weak definition of "privacy" or a relatively exotic definition of "usable". If you're at the point of installing an OS like Gentoo just for its privacy benefits alone, I'd say you're already the latter case, even from the perspective of most fellow Linux users.

Of course, that doesn't necessarily imply very un-private software is always very usable, or that highly privacy-respecting tools with good UX don't exist. Just that most highly UX-polished software tends to have poor privacy, and most privacy-focused software expects the user to do a lot of hoop-jumping to make up for all the systems and workflows the user can't utilize due to having some dealbreaking non-privacy-respecting component to them.