"A little bit" is an idiomatic expression that usually refers to a small amount or "smallness." Examples: "it bothered me a little bit more than I admitted" (to some extent) ; "we talked a little bit" (for a short time) ; "we ate a little bit of dessert" (amount). With "kind of" you are trying to describe something but you can't be exact. "Kind of" is often used to "tone something down." In other words, the speaker knows what the facts are but wants to be kinder and/or discreet when saying them. So... "he's kind of smart" (he's not smart at all) ; "she's kind of sweet" (I like everything about her) ; "it kind of smells" (we don't like the odour). As you can see, there are differences and subtleties that make English learning so much fun... ha, ha. Good luck with your learning goals.

It is used when you want to describe something or explain something, but you cannot be exact. It introduces some degree of uncertainty into it. He is kind of smart = He is a little bit smart, as you suggested. It means that some things he does show that he is smart, but there is some doubt because other things he does are not very smart. It is an informal phrase used in everyday speech, but I would not use it in any form of formal writing. Other examples: He kind of sneaked up on us I'm getting kind of tired, let's start again tomorrow

thank you so much.