Disclaimer: we haven’t done anything with Ignition Edge in production yet.
But you should probably check out the difference between “Edge Panel” and “Edge Enterprise”. See https://inductiveautomation.com/whats-new-ignition-edge
On “Edge Enterprise”, the edge device connects with a regular gateway, and can sync data using the store-and-forward as usual in Ignition. So it doesn’t act as a plain OPC server, but is tightly integrated.