How would you describe them? Logically, some will have to be practical, others will be dreamers, given that reflects life generally (and fiction is a wonderful mirror held up to reflect what we know and experience daily, even if the setting of the story is a fantastical one).
Think about the profession of your characters. What would they need to be able to be organized? Do they aggravate the dreamers? (I strongly suspect the dreamers would aggravate them! There would be good stories in situations where planners and dreamers must work together to survive. There would be plenty of conflict there but they would have to overcome all of that to live. Could be fascinating to read how they did it).
Do your planners come from a long line of planners or are they rebelling against a family that never planned anything? Have they learned to plan because of bad mistakes made by not doing so before? Can the dreamers show an unexpected practical streak when push really comes to shove? Could be some good ideas and stories to explore here.