so it would be better for me to install the panels over the existing metal framing, then fasten the insulation panels to the framing, rather than installing insulation panels between the framing?
Yes. Between can work, but it will have multiple drawbacks. Heat will be conducted in/out by the metal framing, but worse it will allow condensation to form at the edges of some of your insulating panels. This can draw bugs and mold etc.
One sealed envelope will help seal the wind out and will also be a neater install in my opinion.
