싶어요 vs 싶어 해요
What is the difference between saying 싶어요 and 싶어 해요? I've heard different explanations from different people, such as 싶어 해요 is for 3rd person, 싶어요 is more intimate, and 싶어 해요 is used for specific things, but none of these explanations make complete sense. I would also like to know if there is a general rule for the use of 해 with other verbs, such as 좋다 and 슬프다. Thanks!