Prior to installing and configuring I wanted to explain what we need and then the question of a single DB or multiple DB direction might be answered. (note all sites are brand new and will be running joomlart teline III with many of the JA extensions)

we have a master site (news1)
we have 19 slave sites (news2-news19)

during normal operation news1 would display content from (news2-news19). this includes hot topics, most read, search function etc.

news2-news19 would display their own content

which is the best general configuration approach?

Thanks in advance, we are very excited to see if this product will work for us.

With JMS, there is no aggregate or merge of the data of the different website.
If you want to display in the master 'news1) the aggregate of the hot topic, most read modules, search module or similar, this will not be possible.

The only thing that you can do is use the "Article Sharing for JMS" in your master website and create as many menu item to display the articles as you have slave (menu item "news2" to menu item "news 19").

Another approch would be to use an extension like "K2" that allow sharing all the articles betweens website. But in this case, the slave "news2" to "news19" will have the same articles.
The "K2" should be modified to add a filtering depending on the slave site "news2" to "19".
This is kind of filtering require to modify the K2 and create a specific one.
If you want specific development we have a billable support that you can order at www.jms2win.com/download?page=shop.produ...35&category_id=1