It wouldn't make sense for a state legislature to promote a popular delegate election subsequent to deciding an amendment convention was needed to correct specific problems. Re-read Article V: when the legislatures of 2/3 of the states ask for a convention, Congress calls for the Convention. So it is Congress,, not the state legislatures, which will set the rules for holding the convention, selecting the delegates, etc.
The link in #2 has a section about 18th century conventions. The convening authority never set their rules.