1) form width is the width set in the css for the form itself. If left blank it will stretch to fit the interior contents and not the container tag. If you want to fill the container you would have to set it to 100% or the width of the container tag. Certainly adjusting any css styles could effect how the form displays.
2) the formitem container is consistent for all forms, so it isn't changed by any of the settings.
3) fullColumnGroup is the width of the form in a single column layout... the width isn't specified so it should stretch to fit the content up to the available space. It is also used for the second column in a two column layout so that it will stretch to fit the entire form width.
4) error group is a container tag. It's main purpose is to make sure that the error messages align correctly if they wrap to the next line.
5) field group is edited in the them under "form elements" -> "element groups"
6) the actual width of each of these (small, medium, large...etc) are set in the them. Choose "Form elements" -> "Text" and then for each size you can specify a width and other attributes.
7) It will not inspect hand edited changes. Once you start editing the form by hand you will have to continue to, since edits by hand will be overwritten when reapplying.
We hope to expand on our documentation to help clarify some of the features and things to look out for in the future. Let us know if you have any more questions.
