It depends on what you mean by 'work'. Any Android Wear watch will pair with your V20, as will the Tizen based Gear S2 or S3. You will receive call and app notifications, reply to texts etc via the Bluetooth connection. Some watches have sim chips. If you want to be able to answer and make calls with your watch, then you would need one that has a sim chip in it, and is compatible with your carrier network.
The Gear S2 is still a really good watch. I have the S2 Classic and I really like it. If you read up on the reviews, there's really not much difference between that and the S3 outside of Samsung Pay being able to work independently from the watch without a Samsung phone.