Building a system that could accommodate all devices starting up simultaneously would be prohibitive. It is also very unlikely that this would ever happen in reality as most start up surges only last for a few milliseconds. However, it is a good idea to try and offset startup surges. For example, if you use 2 microwave ovens for cooking, start the one and then wait at least 10 seconds before starting the other. This is good practise in general.
You can also ensure that other devices that consume a lot of power are not operational while, for example, cooking. By having the geyser on a timer, you can ensure that the geyser cannot switch on during the times that you are preparing meals.
The bi-directional grid connection is not a useful feature for a grid-tied system that experiences high levels of outages. In other words, it is not suited to life during South African load shedding.
In order to implement the bi-directional grid connection safely, the system using a CT (current transformer) installed just after the customer side of the meter. This is used to create a point at which the system can prevent power from being exported into the grid. The system also requires the presence of the 50Hz signal from the grid for the grid connection to allow power to flow. This is where the problem comes in. You may have plenty PV capacity available for anything connected to the grid connection, but if the system does not detect the presence of the grid, even if you are not consuming from it, the grid connection on the inverter is disconnected. This means that not only do you lose out on any FIT (Feed In Tariff) revenue that you may have got from exporting, you also cannot power up any local appliances connected.