One of the first new features is 4 new watch faces.
Astronomical New Face
Lunar New Face
Playtime New Face
Metropolitan New Face
Activity Rings What is New
Running is getting an upgrade in watchOS 9. Vertical oscillation is one of the new features to track u in the new update & stride length is the second new feature the last one is ground contact time. Finally for the tri athlete if u finish swimming and going to running it will switch automatically. And if u don't have a watch but u want to close rings the fitness app will be on all iPhones.
Next, what is new with your sleep.
The Medication app will help u better take your meds by reminding u to take them at the correct time & u don't need a watch to do it. So to put your meds on the iPhone u don't have to type it in but use the camera to scan the label.