Perhaps this is why Apple has outed new promo videos for the Apple Watch Series 4 that are detailing how to use precisely those two functions. The ECG one is coming with a future update anyway, and fall detection is kind of self-explanatory.
Given that the new Apple Watch Series 4 sports automatic workout detection, as well as new workouts such as hiking and even yoga, it's good to learn how to use this option straight from the horse's mouth. That's not to mention the advanced features for runners like the new pace alerts, too.
The Emergency SOS function has also proven its usefulness numerous times already and is perhaps the first most important thing you need to learn to use on your Apple Watch in case you get into any kind of trouble that would require alerting family, friends or the authorities.