is it possible to create a weblog on my existing EE installation, assign categories and so on, and when finished with design and content, then set up the subdomain and insert the path.php and the index.php with the appropriate variables pointing to that weblog?
Yes. The first step is always to figure out the structure of the content and get that content inputted into the CMS. Then, you can design templates using your current installation of EE, and then “move” them over to the subdomain later.
Also, does it make sense to just have one weblog and create cagetogories named after the months and then limit the content output on the home page to that month/category?
It seems like you might be making this a bit harder than it needs to be:
In Joomla, everything is based on “sections” and “categories” of information. Joomla is very confining in this way. EE does not place limitations or impose structure on the information in weblogs. Rather, you can do whatever you want with that information.
So, in Joomla, it looks like you have generated the various issues of your magazine using Joomla’s sections. In ExpressionEngine, it is not necessary to structure your weblogs this rigorously. When you input the various articles, you will use the “publish date” of the weblog post to assign a date to each post. Then, you can easily use EE’s blog archiving features to sort those posts by month, year, day, etc.
This is the statement that caused my lightbulb moment: In Joomla, the data is STORED according to its intended presentation. (Articles in an issue of a magazine are in a rigid section for that issue.) In EE, the data is stored all in one place, but PRESENTED according to its intended presentation. (All your posts will be in one big “magazine” weblog, but you will be able to divide them up using templates when you present them to your users.
Does that make sense?