I'm interested to know what responsive design features Xenforo has. By this I mean features that allow xenforo to be automatically viewed on a PC, mobile or tablet without users having to be diverted to a separate mobile site for mobiles or tablets.
As long as you have enabled the responsive setting for your style and its set up correctly, yes, that is what responsive design means. If you'd like to see it in action, resize your browser and watch how the style changes and smaller widths.
Best thing to do is resize your internet browser. You can clearly see the responsive design take effect.
The basic premise is a lot of elements are now maximum width instead of fixed width or use percentages. Then on top of that you have media queries that can remove, move, resize and do many other fancy things based on the view width of the browser.