K2 items can be displayed in a responsive way. T3 framework and template absolutely support that, but usually that's not enough for a responsive result. You may also need to modify some less or php files related to the k2 component. If you are not familiar with coding, you could choose a template with built in customization for k2.
A nice choice is http://www.optimumtheme.com/demo
/ They use t3 (which is great), k2 items, and many more