You rub the iphone on your head and it magically tells you
This is why I hate apple products more than android. Both lock you out of seeing important stuff, it seems it would hurt the brains of stupid users who have to know anything technical.
It all depends if you can find a APP that will display resources being used by other applications similar to the resource manager in windows. It all depends on what the phone os allows software to access.
If your router supports tcpdump, which is kinda impressive, it like also allows you to block traffic. Block the port and see what breaks. Maybe the ip address on the internet will also give you a clue. Unfortunately you see many ip going to hosting centers so it does not always help