SydneyPaula

Have you heard of Sydney Greeters? That might be a good solution. It's a free service where a local volunteer shows you around for a few hours or even a day. They can help with suggesting things that are accessible if you have any specific requirements. Book a month in advance for the best chance of getting assigned a Greeter. https://sydneyexpert.com/introducing-sydney-greeters/

Optus is fine for most travellers especially for coastal areas. Once you hit the red dirt it's gets less coverage. We did a 5 week tour in South Australia and 5 weeks around NSW with Optus and only had shirt periods with no coverage. As someone mentioned above there are mutiple companies to use but they all run via Optus or Telstra This is a useful guide https://australiayourway.com/australian-tourist-sim-cards/