Can I customize the design of the bundle template (no-code)?

Yes, you can change the design of active bundles via Dashboard => Change Design. 

All bundles share the same template, which can be customized in the Shopify theme editor. For example, you can change the button color to match your brand. The experience is the same as customizing your product pages since we're using the same static Theme Section feature. 

The sections beginning with " BYOB" are developed by us. When you hit the Save button, the style is changed immediately. The gif below is customizing the template under the free Debut theme offered by Shopify. 

For the latest Online Store 2.0, you can even add sections to our template. For example, you can add an image or text after the product grid.

Note: We're adding more options from time to time. The above screencast doesn't reflect all available options.