In 1700s terminology, the process of regulating (training) the militia has to take place after first gathering the 'irregular' militia, whose members bring their own weapons. This was established even in colonial times. https://en.wikipedia.org/wiki/Regulator_Movement_in_North_Ca... You'll recall the Baker Street Irregulars, and Paul Revere's "You know the rest, in the books you have read, how the British Regulars fired and fled." The 2A's 'Arms' also covers non-gunpowder weapons. The right of the People to keep arms comes prior to issues related to their use.

"Well-regulated" in the context of 18th Century American English refers to the object's character, not to a system of regulations.

You might say that a farmer runs a "well-regulated farm" because things run smoothly. Or that the windmill was a "well-regulated machine."

The point about militia is a short statement for why the right to bear arms is important, rather than trying to restrict or qualify the right.

The ability to form militias is so important, that everyone should have the right to bear arms, in order to enable this.

The idea is that it prevents the idea of a "special militia" having some selection criteria, so the government of the day cant make qualifying for its group a requirement to own guns.