Hi,
Note that for the upload of the product and category images, you can change their size automatically thanks to the "Image resize during upload (width x height)" setting in the HikaShop configuration. It has been there for years.
And for the image optimization, I would actually recommend goin with something like this:
extensions.joomla.org/extension/imagerecycle-image-optimizer/
Not only will it work for the images you upload in HikaShop, it will also work with other images you have on your website, for Joomla articles, other extension, etc.
This looks better to me that if we would integrate with such service only for HikaShop images.