Create log only on traffic from a certain IP?

Not directly within the plugin, but you can write some custom code using the “wp-rest-api-log-can-log-route” filter to always return false, but have it return true for specific IP addresses.

For reference: https://github.com/petenelson/wp-rest-api-log/blob/develop/includes/class-wp-rest-api-log.php#L81