1) Ajax search results speed depends on server response time and optimized structure of your DB. When you type anything site generates requests to get results and if your server response is quick then you get them immediately. On your site it takes up to 8s to get response http://prntscr.com/qeqs3m and compare to our demo where it takes up to 200ms only http://prntscr.com/qeqvsi So, contact your hosting provider and ask them to reduce the server response time.
2) Our theme does not have search by category title, only by the products, product SKU, pages, posts. If you want to have any other types of search (by category title, tags etc) you need to look for additional plugin or submit additional customization requests to WPKraken team.
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