In what situations and styles do you designate crusting buttercreams, egg white/all butter buttercreams, ganache, and american buttercream.
Now let me give some details so that we are all on the same page.
Crusting BC - any kind of all-shortening BC that yields a crusted like shall that can be softened at certain stages with a paper towel or misted to give a shiny look. Shortening in BC often leaves an unpleasant feel in the mouth, but increases it's resistance against heat and humidity.
American BC - regarded as a quick-whip recipe, american bc is a fast to make but almost always yields a high sugar taste, thick but creamy and maneuverable BC. Comes in all butter, all shortening, and a hybrid.
Egg white/ all butter BC - Swiss, Italian, and french BC are regarded as time consuming, but yielding a light, fluffy, softly sweet product that spreads easily and refrigerates into a solid state.These traditional BC are usually all butter made that give them a mouth melting taste but makes them vulnerable to high temperatures.
Ganache - a chocolate/whipping cream ratio that produces a creamy chocolate, able to be used as a filling and as a coating. The flavor is decadent and the product refrigerates in a solid state. Ganache is susceptible to high temperature and traditionally cost more to make then a BC.
With these characteristics in mind, do you use certain icings for certain project. I was making a sculptured cake and thought to myself "which icing would yield the best result for this?" but why not make a list about everyone's application of icings.