The degree to which you break down your page into seperate editable areas is entirely up to you, based on the logic of the page dynamics - i.e. there may be areas that will require regular updating, and it would make sense for each of those areas to have its own inserted developer's code, as the styles that exist for those areas in your page's stylesheet will be inherited by the editable areas in the CMS. There may also be areas of the page design that will not need to be updated.
It may also be easier for your clients to administer the updating process without 'breaking' your design if you use more rather than fewer specific areas.
Having said that, this test page has only three editable areas, two of them in the side bar, and the third being the entire main content area, which I would be happy with if it were me doing the editing. If it were a client doing the editing, I would want to break it down in to individual areas to ensure that the internal design structure of the content area remained intact!
Incidentally, the way I did that was to copy all of the content area html code and save it to Notepad, then delete it from the page html and replaced it with the developers code for the editable 'content' area. I then went to the CMS Admin update pages for that page's content area, selected 'Source View' and pasted in the original html code out of the Notepad doc.
If you paste the code between h1 tags, then all text will be in h1 format unless that is changed from within the CMS. You could leave it like this if it was a Section Title that was going to be regularly updated. Generally though, I think it would be best to place the code in areas with normal page text properties, and add any special formatting as required from within the CMS. You can also set up the HTML Editor to add your own page styles to its 'Style' toolbar select list.
You can create your areas with the developer code in place without any text or content if that makes sense - and it often could - but in practice I've found I have to enter a couple of spaces in the CMS' WYSIWYG area otherwise the new area won't save.
Not sure if this cleared anything up, but the bottom line is that you can set up things exactly as you want them, based on how you foresee the practicality of the page updating and your clients' abilities.
Please post back with any queries as and when required!