At this point you need to decide what works best for you. With most of my companies, because they aren’t supremely complex and are hosted on major platforms (Shopify and Woocommerce) I opt to just install a (paid) plugin.
The reason for doing this is strictly because my time is worth more than the effort required to deploy a comprehensive EEC tracking strategy via GTM.
That also being said, there are times where this becomes a problem, especially if I have a product or offering that isn’t your typical e-commerce or product offering.
For Shopify I recommend Elevar although it is a bit pricey at $50/month for the starter plan – it also includes things like Facebook Conversion API support which is critical to the future success of e-commerce.