As soon as I started teaching courses on my reading method (since 1999), students would ask me why I placed three cards at the beginning.
I would explain to them that my method is based primarily on two basic rules, which I call the "Law of the Solution Card" and the "Law of the Regard". Also that at the beginning, one could start with whatever number of cards one wants. One can place three cards, four cards, five cards, or more. But the number of cards one begins with governs the energy of the reading.
Personally, I practically always use the "three card alternative". That is the one which is connected to the Sacred world and which resonates perfectly with the laws and the secret codes of the Tarot.
But, just on occasion, it can be interesting to use the other alternatives…Philippe Camoin