Hi,
The content tags only support products with a public access level.
Now even if we were to implement the capability to handle products with specific access levels, what it would do is that it would hide or display the whole product are based on the user groups of the user, not just the green add to cart button of the product.
But you could reproduce this with a content tag plugin like this one:
extensions.joomla.org/extension/access-a...cess/content-filter/
Now for the add to cart button, if you configure your product's prices so that no price is available for some user groups, and you have the "display add to cart for free products" setting turned off in the HikaShop configuration, then the add to cart button will be removed automatically for these user groups. So if you only want to target the add to cart button display, this would be what I would recommend to use.