Welcome to the forum.
I own a similar camera, don't own a Mac and don't use CS5.5 or 6. Instead I use a PC and have been teaching myself the $80 Adobe Premier Elements 11. I still might be able to point you toward some answers.
First, read up on AVCHD. Wikipedia has a good summary. Then see if the section in the manual on format choices makes sense.
Your choices for settings are listed here, with the highest quality on top:
1080/60p (28 Mbps / VBR), (1920 x 1080/60p)
HA (17 Mbps / VBR), (1920 x 1080/60i)
HG (13 Mbps / VBR), (1920 x 1080/60i)
HX (9 Mbps / VBR), (1920 x 1080/60i)
HE (5 Mbps / VBR), (1920 x 1080/60i)
iFrame (28 Mbps / VBR), (960 x 540/30p)
You can see in the list the Mega bits per second. The bigger the number the more "detail quality" in the footage. P is for progressive and i is for interlaced, with is a confusing concept left over from the invention of broadcast TV displayed on TVs with tubes in them. I know nothing about iFrame.
Notice that the highest setting is 1080/60p. It was added to the AVCHD standards later than the rest of the settings. So, you may not find it in 5.5 presets. My last version of Elements didn't have it and I found that a 720p preset worked fine. My understanding is that the presets have mostly to do with the real time editing preview and a lot less than the final rendering to your delivery media.
It may be that with 5.5 you will have to work with the settings other than 1080p.
Since you said your two primary choices of delivery are DVD and the Web, all the other settings should work unless there is fast motion like in sports. DVD is standard definition (SD) and the output rendering will have to lower or "down rez" the picture quality. There is plenty of reading on that process in the Adobe Premier Forums (http://forums.adobe.com/community/premiere
The current version 11 of Premier Elements does all the work for you. It automatically picks a preset based on the first clip used and burns DVDs from within the program itself.
For the Web, video is usually delivered with YouTube or Vimeo. Both have specifications explained on their sites. The idea is that at final output rendering you try to match the specifications because it improves upload times. However, if you have the bandwidth or the time you can up load almost any format and it will get converted to required specifications.