They have to have the same numbers of elements, or the element-wise multiplication will throw an error. You can multiply one as a column vector by the other as a row vector using matrix multiplication (not element-wise multiplication) to create a matrix.
If they are the same lengths although different frequencies, they willl produce a ‘beat’ between the two of them essentially modulating each other. (This creates a double-sideband-suppressed-carrier signal.)
