Point of roaming is that I want the data, not the calls. And the reason I want a separate SIM (eSim or a physical in my spare phone) is so my usual number remains active if its needed.
Yes, a local sim is one way to go, although I prefer to be all set before I leave plus I hate faffing around getting stuff on arrival at airports. Just a personal preference. When I have a driver, I get them to stop off somewhere and I get a local SIM off-airport. Driving myself, I like to just get going.
Do you think Optus uses its own network overseas?