For Shopify to work effectively with Tagrain do I need to rely upon other plugins?
No, this Plugin is independent. Tagrain can integrate either to a new Shopify site or an existing Shopify site via the Tagrain Shopify Integration plugin in Tagrain.
Plugins in Tagrain are either Subscription Based or License Based. So the price that you pay for your plugins is based on the number of POS terminals that you have in your setup and the number of licences that you have acquired.
There will be no change in your subscription amount in the current billing cycle if you are only deactivating the Tagrain Shopify Integration plugin AND not updating your Store / POS count.
The Tagrain Shopify Integration plugin is not available for activation if you are running the 14-Day trial evaluation of Tagrain.