Learn English – Using “Would you like” vs “Do you want” between friends

This expression by nature is very personal, so you'd never see a "formal" version of this expression. This is a light-hearted way to ask what someone's hopes and dreams are. It is about as polite as you can be for this sort of question. Asking someone what their passion is, for instance, might demand a serious response whereas "What floats your boat?" is flexible and allows a non-serious answer, making it all the more polite to use than an alternative.

Though that said, here are a couple alternatives: "What drives you?" "What's your passion?" "What do you do for a living?" (not precisely the same thing, but you might get an equally in-depth answer)

All three are grammatically correct and I don't think any of them sound odd. Number 1 is the most concise and so I would generally prefer that.

We often ask "would you" or "could you" instead of stating what we want the person to do to be polite. Like, "Would you put that back in the box when you are done with it?" is a polite request. "Put that back in the box when you are done with it" is an order and might be considered rude.

But "do you" makes it a question rather than an order anyway, so is just as good as "would you". And making a suggestion is unlikely to be considered a chore, there's a certain implied compliment in asking someone for a suggestion, so there's not as big a need to make it more polite. "Send suggestions to xxx@example.com" probably wouldn't be considered rude even though it is phrased as a command.