Both "how about" and "what about" can be used like 呢. "你呢？" = "How about you?"/"What about you?" "How about" can also mean "let's..." or "why don't we..." It's similar to 不如. "How about watching TV?" = "不如看电视." Usually, we do not use "what about" this way, although it does sometimes happen in casual speech. Examples: A: "I like drawing, reading, and riding my bike." B: "What about watching TV?" A: "Oh, yes, I like watching TV, too." [In this example, you could use either "what about" or "how about." Person B is asking, "And (do you also like) watching TV?"] A: "What should we do tonight?" B: "I don't know. How about watching a movie?" [We use "how about" here, because it is a suggestion: "Let's watch a movie."/"Why don't we watch a movie?"]

In my opinion, "how about" would mean only 1 choice is offered. And I think "What about" means offering ANOTHER choice into the mix. EXAMPLE: PERSON 1: What do you want to do tonight? PERSON 2: How about we watch some TV? PERSON 1: What about playing board games instead?