Solar connects to your home’s electrical supply and the local electricity network. The connection approval can set conditions on how much unused electricity you send to the grid. That is an export limit, and it is different from the amount of electricity your panels can produce.
Ask who handles the connection application, which approval the quote assumes and whether any meter or switchboard work is included. Confirm the network for your address from your electricity bill; a suburb name alone should not determine the connection conditions in a quote.
The number of panels is only part of the decision. Compare the roof layout, inverter, predicted generation and your likely daytime use. Savings also depend on your electricity use and rates. Read the Australian Government’s connection guidance.