A Shopify store is not a marketplace, so nobody collects TCS or prints invoices for you.
Shopify is not an e-commerce operator under Section 52 for your own store, so there is no TCS and no Table 14; your sales are ordinary B2C or B2B supplies in GSTR-1.
Shipping goods to another state makes registration compulsory under Section 24(i) regardless of turnover, which covers almost every Indian Shopify store.
Every order needs a tax invoice under Section 31 at dispatch, with the place of supply taken from the shipping address; refunds and RTO are credit notes against that invoice.
GSTR-1 (Table 7, 5, 4, 9B, 12 and 13) and the GSTR-3B summary come from those invoices, filed by the 11th and 20th, with ITC on gateway, courier and app invoices matched to
No. TCS under Section 52 is collected by an e-commerce operator that owns the platform through which other suppliers sell and that collects the consideration.
The full guide has the formats, the deadlines and the worked examples.