I created a little 'behind the scenes' resource on how I set up a responsive design system for a team of designers to use in Sketch. Also included is a small insight into the documentation. It includes two downloads featuring one of the patterns in the system.
The Sketch download demos a responsive UI, featuring a small subset of form elements and text styles. If you select the text input symbols you'll see that you can change their state, or switch to a different type of input, retaining all your label and data values. It's only the very tip of the iceberg, but I hope it gives some insight into the potential of the full system in Sketch.
There is also a PDF download featuring a small excerpt from the documentation for the pattern featured in the Sketch demo.
I hope it helps :)