shopify customization, Now using shopify app

Hello! I am setting up a new shopify store where I need a solution for product customization with mock up preview. People should be able to choose tshirt size, color, and then cat breed and color of the print on top, and they should be able to add name of their dog on top. This all should be showing on the mock up preview in store in the selected combination. I am using a shopify app now, but with this app the website is far to slow. I need either optimization of the app, or a custom code programming or another solution you can offer. Kind regards, Price is 60$ Fixed