The JCH Optimize plugin does not assist with reducing server response time. In our article, How The Plugin Speeds Up Your Site, we explain that the plugin reduces the time it takes to download the HTML by optimizing the HTML of the site. The server response time is mostly caused by the time it takes the website to generate the HTML. Caching can help in this regard. Since most parts of the output is the same on each request, caching saves this output for a specified period of time then serves the saved output on the next request rather than performing time consuming processes to compute then serve the same output again.
If you are experiencing high server response time however, this can be indicative of an unusual problem on your site. These are generally caused by either a very slow server, probably unsuited or improperly configured for your needs, or some inefficient software running on your site. Before employing caching it may be profitable to properly investigate these possibilities.