Bigcommerce also has a nice library of themes for you, divided into multiple categories, and all of them responsive and fully customizable. They were developed to establish a more modern, fluid user experience, utilizing cool new merchandising features for categorization and differently sized catalogs. There are both free and paid options available, and I have to say that those free ones really are attractive-looking.
BigCommerce is most easily compared to Shopify. Both platforms offer a similar experience when building an ecommerce platform. Like Shopify, BigCommerce offers a range of prices and packages tailored to different types of businesses. The platform is highly customizable if you are comfortable with some light coding. It is also possible to use themes and templates to build your website, but some of these will come at an additional cost.