Our components are initialized in an asynchronous manner, which means that the page load is never stopped to wait for our servers' response. We send a request to our servers on the page load, and allow the other parts of the page to continue loading. Also, when our server sends the response (i.e. Recommendation boxes' contents) back, we just fill in the boxes.
When you enable the review apps to show in the recommendation boxes, this may affect the page load time since Shopify does not support batch loading. Shopify's API makes the apps load the reviews one by one per product in the recommendation boxes.
Lastly, the image sizes in the recommendation boxes do NOT affect page load speed at all. Our app is using HTML5 (ie. 'srcset') which introduced a new technique for responsive images to address different devices and screens. We have used this technique so that our boxes use the correct size and pixel densities depending on the size of the screen. This new technique creates an attribute that supplies a list of files of the different image sizes. The browser decides which file to load and display on the device. Therefore, this technique does not affect any page load speed.
Please be aware that our tech team is consistently monitoring the load time of our components and frequently performs optimization updates.