Update headings plus edits for consistency and clarity in Config Reference

Partial-Bug: #1250515

author: diane fleming

Change-Id: I92c9ad25ee5bbd2c9334c4860637faa1b358718b
backport: havana
(cherry picked from commit b417259465a50db01ff16deaca00c5f60ed8b315)
Merge "Update headings plus edits for consistency and clarity in Config Reference" into stable/havana