Depends sink placement within the vanity, so post a picture

You want to place lights in a way so when someone is standing in front of the sink there is no falling shadow on that persons face. Even if you use a single mirror over entire vanity you should have a light for each sink.

If you using 2 mirrors and the vanity is located in the middle of the wall you can use a light over each mirror or a light on each side of the mirror.

If there is a wall on one or both ends of the vanity then you would usually use a light over each sink.

Good luck

Thank you! My original thought was two separate mirrors and two separate lights but wondered if that might get a bit too busy. Your input has me leaning back to the two mirrors and two lights. Thanks again.

Sorry can't post pics, vanity is still in its crate and we are waiting for mirrors to arrive....thanks!