How can one differentiate between the obsessive doubt (waswas) of urine drops exiting and urinary incontinence ( سلس البول – سلس البول), and what action should be taken regarding that?

If your feeling of urine drops exiting is merely an illusion, then it is a waswasah (whisper from Satan) that you should ignore, and wudu' is not invalidated except with certainty. However, if you are certain that urine exited after relieving yourself, you are not considered to suffer from سلس البول (urinary incontinence) unless the discharge is continuous, such that you do not find enough time to pray with proper taharah (purification).