Creams come in several formulations, but roughly we can divide them with either fat or water as dominant source when we start. If we can incorporate air into the cream we can create air to become the dominant source at the final product. Water, the type of fat (or oil) determine what other ingredients to choose in order to achieve your goal. The amount of air we put in creams will determine how well we will perceive them, however this remains co-dependent on the other ingredients present. Generally speaking the higher amount of air in a cream, the lighter and airier and therefore a smooth experience will take place upon consuming this cream. If however the cream is used as a layer in between layers of cake or biscuits a denser version is required as more air means also more instability in these cases. And a sandwich biscuit that separates from its cream or a celebration cake that collapses is not a great signature of your capabilities. This is why in cream for biscuits little to no air is being used.