Well, most people fall into the clan where they are placed. I guess that's just my prediction of where you'll end up if you so desire to join one.
However, a few of my friends have switched clans and fit much better in the new clan. Most of the time, though, you'll get the right clan from the outset like I did.
I don't see why not! Great White North was clanless for five years and joined din recently. He loved it. Pietro was clanless for eight. After he joined, his posts went from 2400 to 2800 in a month. He used to never post! My friend Golddron left clans for 3 months. He hated it. Lol thats from what I've heard anyway. It's completely up to you.