It depends on your local network provider (Ausgrid does most of Sydney I think) and what approval you can get for more solar generation. I’m not familiar with Ausgrid so hopefully someone local can explain. Here’s a link to Ausgrid’s application… Ausgrid - Apply for a connection
Enphase Micro-inverters are a great option but will not make any difference to how much you get approved or whether you need to upgrade to a 3-phase supply. Micro-inverters can be easily export limited but so can any solar inverter with an additional consumption energy meter.
Other options could be to install battery along with the new solar system and have zero export on the new system. If you have high consumption you may not need a battery all. If the new solar system is mostly for self-use (air-con, pool pumps etc) then maybe get a zero export and save the hassle of upgrading to 3-phase to get more solar.