对于数据成员，如果包含对象已经在动态内存中，那么动态分配此变量（或不是）之间是否有任何区别？

I'm starting with the assumption that, generally, it is a good idea to allocate small objects in the stack, and big objects in dynamic memory. Another assumption is that I'm possibly confused while trying to learn about memory, STL containers and smart pointers.I'm starting with the assumption that, generall