native SD DV is 720 x 480. Capture and Sequence settings should be this. Yuu can resize your Camtasia to whatever you like, either within Final Cut by scaling, or by exporting from Quicktime player.
Not sure what your final output is, so it’s hard to say what to export at. If it’s a DVD….just export as DV, if it’s something different, just try to keep the same aspect ratio (360 x 240, etc.) so things don’t get squished. Hope this helps.