When playing in G, most G/C players will use the higher octave of the G row
(buttons 5 - 10 approx).
Yes, G/C boxes are favoured by players on the continent who play them mostly in the top octave. The continental playing style also differs from English style in that it is played much more across the rows rather than on the row. If you are used to playing one style, it can be quite difficult to get used to the other, and you will generally tend to fall back on the first style you learned as being your "natural" style.
So, playing G/C is not the same as playing C/F or D/G (both of which are generally played in the lower octaves). The keyboard layouts are the same on all these boxes, however.....they are just in different keys. There is nothing to stop you playing a G/C in the lower octave...you will end up with the same tune as if you played it on a D/G, for example, but it will come out in a deep,rich growly key. In the same way, you can play continental style in the upper octaves of a D/G or C/F, but it can sound a bit high and squeeky unless you have a 3 voice instrument to provide a reed in the lower octave.
