1. If you load a draft from posting pane on the next page sandwiched between the draft selection and the review panel is a posting pane with no buttons to submit, preview or save as draft. 
2. Editing and saving existing draft in posting pane creates another draft.
3. In UCP under manage drafts you can open the draft using basic editor in UCP. This does not create new draft when saved but it's redundant to the full posting pane.

In regards to 2 and 3 suggest removing the basic editor in favor of the full editor, edits to existing drafts regardless of where they are loaded from should not create new draft.