Last week I heard a compliment of someone having a large vocabulary. Yet the comment they made was not really about vocabulary. They just thought that it was an extensive vocabulary that allowed the speaker to speak precisely.
A large vocabulary has often been as much a hindrance as much as a help. Simple words and expressions are distinctive characteristics of some of the world’s great speakers.
I find that eloquence and precision are best developed by surrounding yourself with language of that pattern. It is absorbed rather than learned. So listen to great speeches, read thought-provoking books, and watch insightful movies. And you might also find excuses to befriend people who speak the way you seek.