@Crusty, please just use the ‘reply’ to add your subsequent posts to the topic to avoid parallel responses, some that might be missed in one or another topical thread when there are multiples.
Our Sydney home has a Daikin reverse-cycle ducted system, circa 2000, that was there when we bought the house. It has only two zones, and around 10 years ago, we put an additional damper on one vent, so that one rarely used room can be totally excluded from its zone.
We are very happy with the performance and control that we have with the system. Recently, I have wondered whether we should upgrade to a newer, more efficient system. We used to do most of our heating with a gas heater, but are moving to using the AC more for this purpose. We have only a small solar array.
When we had the kitchen renovated, the builder suggested that the AC vent in the kitchen ceiling would need to be relocated ( due to cupboards that were deeper and full height ), or better still, blocked off, as any air from the vent is often sucked straight out of the room if you have the exhaust fan running. We agreed, and that vent no longer exists. The duct was redirected to the attic ( the rarely used room referred to earlier ).
The system has only ever needed occasional cleaning of the central filter, and inspection of the outdoor unit.
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I believe there are two levels of control possible. The more basic zone system is you can turn each subsidiary zone on or off but the main zone is always on when the system is on. The second level is you can set the temperature of all zones independently but I believe you are still stuck with the main zone being on. You do have the choice at installation time of which zone is the main one, it doesn’t have to be the “main” rooms of the house.
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Things to consider in Qld include humidity. A ducted whole house system can be zoned for warmer and cooler areas but when it is running the entire house will be humidity controlled. If a single room is cooled the rest of the house can become more humid with the house structure and furniture warming up - requiring more ‘grunt’ to cool it down. In an extreme case that could feel almost like a radiator when the air is cooled but the structure and furniture remain warmer.
I am in Melbourne and have evaporative and 2 split systems, and PV. I was surprised by the favourable electrical load of the splits compared to the (circa 1998 ) evaporative system. The two splits use about the same or less power than the evaporative system until it gets into the 30’s outside - probably more common in Ipswich 
The main gotcha we have with the splits is getting cool air to all the rooms. We have 2 splits with half the house open plan and traditional rooms in the other - one split is a big one in the open plan and the other a modest one in a bedroom at the other end. The ceiling fans push cold air down the hall and into the other rooms well enough until it exceeds 40 out.
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We’re in the Glass House Mountains, and have had a variety of past homes including further inland (NSW and QLD) and tropical coastal.
Experience suggests investing in quality insulation particularly under roof or ceiling should be the first priority. From those houses we’ve lived in with air conditioning and poor insulation the power usage can be 50-100% greater depending on humidity. A well insulated home will reduce the size of air con system required (purchase and install savings) as well as use less electrical power.
There is a wealth of information and view points previously shared in this topic. For somewhere similar to Ipswich we’d be prioritising quality insulation (and possibly forced roof cavity ventilation) in the budget. These costs are offset against a lower cost of which ever system is installed. We’d definitely install reverse cycle for the cold winter mornings and hot landlocked summer days. We’ve found split systems flexible and best for our needs, which included spreading the cost of purchase out over several years. Choice has a guide and useful product reviews we used in selecting our most recent purchases of split systems.
Our modest home has a 5kW nominal (4kW average output) PV system. It is more than adequate for running the two larger inverter split systems on a hot summer day, providing we stagger starting them up from mid morning. For winter we only typically run one system in the morning in the kitchen. PV provides less benefit in winter, when we might run the bedroom air con at it’s minimum setting of 16C. The load on the split system is 300W average per hour. Whether a ducted system can reduce demand to very low levels in winter is worth following up.
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