At some point, the line between an activity tracker and a smartwatch gets blurred. The vivosmart HR+ has many features that are found on a smartwatch, but Garmin is not positioning this device as a smartwatch. It's listed as a "Smart Activity Tracker with Wrist-based Heart Rate plus GPS." I think I'd call it a smartwatch.
If you don't need such a small and slim device, then the Garmin vivoactive HR might be a better buy since it's listed as a "GPS Smartwatch with Wrist-based Heart Rate." The vivoactive HR can run some proprietary apps based on the Garmin ecosystem of the Connect IQ "app store."