There's really no "PTO rep", because there's no "PTO". PTOs are independent, so you're choosing to be a PTA (part of "the PTA") or an independent organization (commnonly referred to as PTO).
As a PTA or a PTO, you might (optional) choose to use services from PTO Today to help you run your group -- articles, expertise, an insurance discount plan, tools and programs -- but that's a separate decision from PTO v PTA.
Lots of info on this site to help you share both sides.