Other Activity GPS Tracking

Did they have you try this? Adding a Custom Activity

Yes, the problem is the "Other" activity does not use the phone GPS.

None of the activities use the phone's GPS. They are designed for Garmin devices. Maybe you just need an app like strava that will record your activity using the phone without the watch

Also, changing the activity type from running to something else, will prevent it from impacting your running statistics. It's not just renaming it, it's changing the activity type.

Running and Cycling are both tracked via the phones GPS. There should be a way to do the same with the Other Activity.  

Running and Cycling are both tracked via the phones GPS.

Guess I need to go back and read the vivoactive 3 manual. 

Did you try changing the activity type in Garmin Connect Web?

use the "running " activity and change the name later however this would affect my running statistics drastically

I didn't check too carefully, but it looked that after changing activity's type - it automatically deleted at least a distance of that activity, from runs' statistics and challenges. I often make run activity and then convert it to walking.

So maybe it's ok? Or have you spotted that some statistics are still saved for primary activity's type despite changing it? And of course you need to change a type (small arrow), not only a title.