Compare the work included in the package, not the number of keywords or backlinks advertised. For a Shopify store, ask for a sample audit that addresses your actual collections, product pages, internal linking and technical issues.
The proposal should specify deliverables, who implements changes, how revisions are approved and what you retain if the engagement ends. Keep your analytics, search reporting and store accounts under your ownership.
Ask what 'quality backlinks' means in practice. Bulk link purchases, guaranteed rankings and undisclosed networks are warning signs. Content should help shoppers make decisions, not simply repeat location keywords.
Set a baseline and review non-branded visibility, relevant landing-page traffic and business results over a realistic period. No agency can promise a fixed ranking or timeline for every store.
If you share your store type, target market and the proposed scope without private account details, it will be easier to compare whether a package addresses your needs.