After reading your situation, I personally suggest that you go for mold design. If you want to mold processing, you should consider it, because the mold is an accessory of the product, and changes in the product will bring about changes in the mold. Update, there are no products that cannot be made, only products that cannot be imagined. Motors are generally relatively fixed, and the structure of the motor is relatively simple. Whether it is a servo motor or a starter motor, it mainly provides power, and the level of knowledge is relatively limited. So if you have good development and choice, I personally suggest you give it a try, of course, interest comes first!