Hi there!
Which extentions you are talking about, please?
We have some eCommerce templates, you can check them from here:
https://www.joomshaper.com/joomla-templates/category/products-gifts
But we don't have any shop extension actually. We have implemented third party extensions within our templates.
So j2store integrated with the Helix Ultimate based templates and VirtueMart integrated with some of our old helix3 based templates.
You can use j2store within your Helix Ultimate as it is tested already.
Best Regards