Hello - (app creator here). I want to clarify my potentially confusing app name choice. This app is not directly affiliated with the website. It’s a 3rd party app that uses the intervals data API to drive its functionality.
For the Strava questions I think you’ll find some answers in this thread:
This question has come up a lot and I’m never totally sure what advice to give, as I don’t want to cause you to end up with duplicated activities. I’ve had to deal with that myself in the past and know how annoying it is. Going forward though you will want to use the native connections instead of Strava. I want to say that intervals.icu will match the Strava activity and still link to it, but I’m not 100% certain. I would try with a small subset of the strava data first to be safe.