Multi-Domain and Domain Mapping

I am new to the site and also to the concept of Domain mapping. I joined your site mainly to learn more about these features. Spending reasonable amount of time on the subject is still not quite clear on some of the basics. I am not planning to do a wordpress.com site. I am interested to manage more efficiently multi-site WP installs. To make it easier here is an example:

Let say I want to setup a multisite install for a products in Germany with germanproducts.com, the products will be in the subdomain or in the subdirectory. Like product1.germanproducts.com or germanproducts.com/product1. The site is setup with a host in Germany (germane IP). In the meantime there is an international site with multi-site install with wordlproduct.com domain name on a US (with US IP). I would want to map germanproducts.com to german.worldproducts.com and preferable “manage” (updated, themes, plugins and create new sites) for all the blogs from worldproduct.com dashboard

To be able to do this in my understanding need bot multi-domain plugin on worldproduct.com (for creating new sites for germanporducts.com) and domain mapping plugin (for map germanproducts.com to german.worldproducts.com). To make this work I need to point *.germanproducts.com to the US IP of worldproducts.com

There are significant benefits of having separate IP for the two domains for ranking both sites germanproducts.com and worldproducts.com with the search engines which are far more valuable than the convenience to manage the network form one site.

So the questions are:

1. When I create a new site from worldproducts.com dashboard using multi-domain (e.g. product1.germanproducts.com) which database will the site be a part of, the US or German? Also under what IP the search engines will see this new site?

2. Can use the multi domain plugin to create new sites in the subdirectory vs. subdomain of the site?

3. If I want to only “map” germanproducts.com to german.worldproducts.com is it necessary to point *.germanproducts.com or germanproducts.com to the US IP?

4. Can the sites were not created by multi-domain plugin, but part of that domain (eg. germanproducts.com) be managed from the worldproducts.com as a part of the network?

5. Do the plugins have to be installed in the mu-plugins or can it just simply in the plugins directory?

Thanks for your help in advance