the combined Qt & engine overhead is about 10MB, so this will be the minimum size of you Application. All the required Qt-libs and dependencies are included within each Application, as other approaches like ministro are tedious for users, which is worth the 10MB overhead. Therefore we are not depending on any other Qt-libs (present or not) on the target device, no further downloads are required for the user. The same applies to every other platform that we support.
Does this answer your questions?