Do I need the StreamLocator browser extension if I have the Hub
The short answer to this is no.
If you have our Hub, you do not need to the extension as well. The StreamLocator Hub covers any and all streaming devices in your home, including all web browsers, so provided you are around the home where you have your StreamLocator hub, then you will not need the extension.
Of course this does not mean you cannot have both. Maybe you want the extension for on the go, to ensure you never miss that latest episode or upcoming football game or your favorite show.