Will the app cause any changes to my store theme?

No, Store Bricks apps not need to modify any of your templates to run nicely in your store.

We use a Shopify programming feature called ScriptTag (see https://help.shopify.com/en/api/reference/online-store/scripttag for details) that allows our app to be injected dynamically by Shopify when a page loads.

While the ScriptTag feature is very convenient, scripts that run that way have to wait till other content on the page is loaded, what can be perceived as the app being slow.

In order to avoid that and load quickly, we provide the option to insert our app script in your main theme template ( theme.liquid). This option is called 'Fast loading' and can be configured on the app preferences page. Please note that this is completely optional, so you can avoid that one-line modification of your theme template by disabling the 'Fast loading' option.