Giuseppe,

Q3 and Q4 both take light and shadow into account, and give a much better result than Q1 and Q2. Of course they take longer to render.

Q3 uses a simpler model, gives a rather good quality, and is relatively fast.
Q4 is a bit better, uses a completely different rendering algorithm, with a slightly higher quality, but with longer rendering times.
It depends on your needs, which of these two is preferable.

Use Plan --> Modify compass and change Latitude to a lower number. Latitude 50 corresponds with approx. Brussels or Amsterdam, but if you change it to a lower value, you will "move" further south towards the equator. This will result in shorter shadows, more light in general, and (maybe/hopefully) a better result.

Hans