Question

How much (peak) power (in Wp) can be installed for system A given the peak power of the inverter and the area available on the shed?

Answer 1

If you consider the rating of your inverter (W) as equal to the power output (Wp) of your solar array, the total Wp of your array should be equal to the rating of your inverter + the losses. The available area should help in choosing the type of module between c-Si and amorphous. For same power output, c-Si modules require less space than amorphous.