Did you think you are the first one raising this matter. Be ensured, you aren't! There are dozens of related threads.
"I see loads of different websites"
Nope, not websites, but domain names.
"Is it possible to find out if a device is doing this all on its own?"
Not with OpenDNS. You had to run a network sniffer within your network.
"Or is it possible to tell which sites have been physically looked at by a human vs an app or PC etc."
Not with OpenDNS. You had to run a network sniffer within your network.