For Xero 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 Xero site or an existing Xero site via the Tagrain Xero Integration plugin in Tagrain. You need to be on a paid TAGRAIN edition to be able to subscribe to and activate the Tagrain Xero Integration plugin.
The Tagrain Xero Integration plugin is not available for activation if you are running the 14-Day trial evaluation of 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 Xero Integration plugin AND not updating your Store / POS count.