Well I am partly author of MakeClothes and I was not able to start(!) a proper documentation until now. But I promised that a few weeks ago.
At least now I started and of course there will be changes in future because all of the tools are not yet final versions.
Especially when you look at your own screenshots, it is MakeClothes, the MakeHuman plugin for blender using socket communication and MakeSkin.
The socket communication will provide the human for MakeClothes, but MakeClothes is also able to load it in another way without the plugin, here my documentation will be improved later, because when I create clothes it is a job for some hours and MakeHuman is usually not running in background then. So I use to append predefined meshes (latest version in my branch scans files in a directory and will propose the meshes found as a base mesh, this software is not yet in the master).
MakeSkin is the program to create materials. Without MakeSkin, MakeClothes creates a simple white material which can be changed in MakeHuman later.
Here is the first try of a documentation;
http://www.makehumancommunity.org/wiki/Documentation:Features_of_new_Blender_pluginSome of your questions will be explained when you read the text (mark as ... buttons). It is possible to modify existing clothes (MakeClothes is able to load an existent .mhclo-file) and I also explained some basics, like what a helper is and what can be used as a human base mesh.
We had so many changes and experiences the last years so that I want to add all the knowledge later into our wiki (like how to create heels etc.). Until then I can only link another article about creating clothes from the past:
http://www.makehumancommunity.org/forum/viewtopic.php?f=14&t=14024