Yaw Yan is full contact martial art. Its a new style started in the 70's. I do not know the current form of Yaw Yan as it has apparently changed. I have had a little training in its orginal form.
I have heard it described as muay thai 'Filipino style'. Basically a hard core approach of muay thai, but fancier. I think this is a fair statement.
In terms of hands it has the standard type of strikes you would find in boxing and muay thai. It also has what are called the bolo punches, strikes based on the movements of the stick( e.g. angle 1 and 2 ). There is also some trapping.
In terms of kicking it has alot more variety of kicks not seen in muay thai (I have seen them in some kung fu styles) which include spinning kicks. The way I would describe a mountain storm kick is a front kick that turns into a downward thai kick.