Aerodynamic may not be comfortable. Depends on your mobility. If you lack flexibility or commute with a backpack or messenger bag, an aerodynamic position may wreak havoc on your back.

Depends on how short you cut your steerer tube. You may or may not be able to move some spacers around and raise the stem. You could buy a new stem that is longer and has a larger rise angle but drastic changes in stem size/length to make a small frame fit will change how the bike handles.

Bottom line. You can ride any bike as long as your feet reach the pedals. But, a properly sized frame will put your body in the best position for good bike handling and efficient pedaling.