Subscription basics please!

[guspasho]

I am just starting out with subscriptions, played around with them a bit, and I have many questions!

Firstly, I was expecting a print or print-like experience when I started playing with subscriptions. Then I noticed that only some provide that and others do not. The Economist provides full articles seems to faithfully reproduce the print edition, but Scientific American is full of stubs and previews instead of anything worth downloading. Does anyone provide a resource for explaining in what ways all the different preprogrammed feeds differ from the print experiences?

And how do I avoid getting multiple copies of the same thing? By default everything is set to download every day, which results in Calibre downloading duplicates every day, not just checking for new content. The content I want are monthly and weekly magazines. I thought that I could just turn on a subscription and I would get monthly and weekly downloads of monthly and weekly magazines. Is there a resource anywhere for figuring out the ideal times for downloading any particular feed?

My experience differed quite a bit from my expectations and I can't find a guide to using subscriptions, so any help would be appreciated. Thanks!