I have the 3021 for shooting outside my studio - love it!

Yes, you can mount the pole sideways (great for getting the camera directly ABOVE flat objects), and even flip the column/center post upside down so you can put the camera REALLY close to the ground. The legs also click "wider" so you can drop the height even more - though this often won't go TOO low as the column will hit the ground (but again, there's the sideways mount to compensate).

It looks like the one TwoPynts linked can go upside down as well.

Danob is right - get a quick release plate per camera you own. They're cheap, and it makes for a fast interchange in the field.

Yes, TomDart is VERY right - get the sturdiest tripod you can afford - you won't be sorry. But you WILL be sorry if you buy a flimsy one and your camera tilts over with a good stiff wind.

Good luck and happy purchasing-
-Lew ;-)