Pretty much yes, you have the right idea. The only one that 'feels' a bit different is #3.
"What do you think?" is a very neutral way of asking things, and a bit less formal (and therefore slightly more common) than "What is your opinion?" or "What are your thoughts?". The first "What do you think?" is something I might ask a friend about whether or not I should eat an extra piece of chocolate, for example, but I wouldn't say "What is your opinion?" or "What are your thoughts?" unless it was a slightly deeper/more interesting topic.