There are three basic forms of bonsai display styles regarding to the Japanese traditions. They are named shin, gyo and so.
These examples take their start point in the cases where a scroll is used. There are plenty of examples of displays where a scroll is not used, but the basic styles are easier to explain by the use of a scroll. In the case of Shohin-Bonsai displays, it is important to note that the overall point is to express beauty and the time of year (summer, autumn, winter or spring). Also the environment can be expressed through choice of pots i.e.
Especially the mood and time of year is suggested by the bonsai and the accent.
Shin is a very formal style, and in this case the scroll always is settled precisely in the centre of a Tokonoma.
Gyo is less formal, and allows the scroll to be placed slightly off centre. This influences at the bonsai style and accents chosen, which also is accepted to be more or less informal in their style. Often this style is used by westerners. Probably it is often due to lack of knowledge regarding the Japanese style and the way to read a display, and partly it may lie in our culture and natural free way of thinking art.
So is the free style, which lets the artist play around more freely with the elements. So allows the scroll to be placed much more off centre, and the usage of more artistic pots i.e. are also in the slipstream of the free form.
Furthermore, just to make it all more complex, the different forms of display can be toned and mixed. And the interpretation of the chosen style can differ from the artists. The point to take is that one has to be open minded to the expressions of the whole composition. A scroll is not a given thing in a display, but it can add mood and underline the time of year in the display. The main focus is the feeling of the display.
The final expression and interpretation is related far more to feelings of the display than following rules. The untold and understated elements are the key to feel the display.