Herewith I can confirm that the Garmin Glo2 works perfectly on the iPhone7+ with Cachly!
The difference in GPS-reception is very noticeable compared to the build-in GPS from the iphone itself. From a dwelling GPS loction under the trees to a fixed location within approx. 2 meters from the desired location. This is pretty much identical to the Garmin Oregon700 and Etrex20x.
Great news, this will enable me to get a precise location on my iPhone running Cachly, no more manual entering coordinates on the other Garmins anymore