Another extremely useful feature is Network latency modifier. You should always test every website on at least a 3G connection, and make sure users can see important parts of your site in reasonable time.
For advanced users, you should NEVER use the Network latency modifier in Chrome, and use something like Network Link Conditioner on Mac. This is because Chrome applies the modifier after all the packets have arrived normally at the client, so testing things like HTTP/2 resource prioritisation becomes a problem.
