If you add a fiend my friend app user to your fiend my friend app, then that other user will be able to track your phone only to be able to know your location/position on a map. Find my friend app doesn't give the option to wipe content of the phone, but also you need to have phone turned on before one can use find my friend to locate you.
At the other hand, if you allow someone to use your apple ID and password iCloud> find my phone/ on your iPhone, then you have no control over what that person can do to your phone, the person can locate you any time, remotely lock the screen anytime, remotely wipe the iPhone anytime remotely send the sound blip anytime, the only thing you can do is to unlink your friend apple ID from your iCloud.
I recommend that you use your own apple ID to set up your iCloud> fiend my phone, and add friends who want to follow your position in you fiend my friend app.
