Finding a suitable size for your system
Each single micro inverter can deliver up to 1800 Wp AC – given that four of your panels can provide that much peak power. This means that 3 inverters will have a peak output of 5.400 Wp. Adding 3 more inverters and 1 more panels will give 10.800 Wp. It is also possible to have other numbers of inverters like 4,5,7. In the latter cases solar energy will be distributed unevenly over the phases of your home grid. This should not bother you at all because your three-phase-grid will balance all differences implicitly. But it is considered good practice to have a difference of only one between the number of inverters connected to any phase.
If you do not get paid for feeding surplus energy and you do not have a battery your aim is to synchronize energy production and your own energy use as best as you can. This means that your panels should be facing EAST/WEST if you are spending energy in the morning and in late afternoon. You should avoid using too many electric devices simultaneously (like washing machine, oven and dish washer).
A simple rule for an installation without a battery says, that 3 micro inverters and 12 panels will be enough if your yearly energy demand is around 3000 kWh. If you use less energy per year even one or two inverters (4 or 8 panels) will be enough.
If the grid is fairly stable a battery is not really necessary. If, however, your grid is off for some hours more than once a week you should add a battery of 5 or 10 kWh. In that case you should use 4 inverters (16 panels) or 7 inverters (28 panels) — with one of them being connected behind the battery, so that it can produce energy even in off-grid periods. This will result in a peak power of your system of 7.2 kWp or 12.6 kWh.
If you are beyond 7000 kWh annual energy consumption you may want to look for an ES-Hybrid system. But in principle it would also be possible to extend an ES-Micro system to more inverters, more panels and larger battery sizes (15 kWh e.g.). If you are willing to use more than one battery charging unit you can build even larger systems. You only deal with low voltages and can do 95% of the work yourself. BUt you should not expect a cost advantage for large ES-Micro systems compared to an ES-Hybrid system of equal size.