I can make you a brand new Shopify store from scratch as per your designed PSD, and it will be fit on every media screen out there (100% responsive). the theme will be completely editable from the theme editor that is you will have full control over the layout, also some apps will be added to extend the functionality of the store (depend on the requirement of the store). the speed of the theme will be faster and will pass the GT-Metrix and google speed insight test, furthermore, On-page SEO can be done so it can be found easily by web crawlers,