best approach to get and display list items in sharepoint branding site

I have implemented a branded SharePoint site for a customer .The customer wants to have some "dynamic" custom list views e.g fetch 3 items from a specific list and show them in a custom designed box with borders, paddings colors and background colors etc. He also wants to have the ability to move this view among the webpart zones ,no static content and also have many instances of the same webpart in the same page to show different lists. So after some thorough research I ve decided to implement some visual web parts that contain only front-end code i.e razor and javascript. My implementation was inspired from this example http://ift.tt/1vsCBEE

I have added properties to the web part like listName,background-color etc so the customer could fill in the right properties and get the result he wants. The visual web parts were deployed as sandboxed solutions. However I am not sure about my approach. I have noticed that the cpu consumption is very high and the page load time is relatively slow. I changed some webparts from sandboxed solutions to farm solutions and I am considering if I should use app parts . Is there a right approach for this kind of problems? What is the best and most efficient way to implement such a functionality?