You can’t identify regular cannabis seeds as feminized or autoflowering just by the looks. Same goes for indica and sativa seeds, or industrial hemp seeds. That's why you should always purchase them from reliable seed banks to avoid seller’s incompetence.
Although most seeds resemble dry rice in size, some are not much bigger than a freckle while others are no smaller than raisins. This does not determine the size or the health of the plants you can grow with them. It is generally (not in every case) true that sativa seeds fall on the smaller side of the spectrum while indica types – on the bigger.