It is outrageous Garmin have not offered a simple Basecamp-like piece of software as an app, basically something like EasyGPS but as an app that, as you say, you could connect your Garmin and phone to via USB. There is a Garmin app but it's only for their Bluetooth GPS devices.
There does appear to be an Apple app that does this.
https://www.loadmytracks.com/Perhaps we should encourage EasyGPS to make an Android app!!