A migration forces a decision most stores avoid: what should the storefront actually look like on the new platform? The temptation is to recreate the old design exactly so nothing "changes." That is usually a mistake, because it ports the old problems along with the pixels. Here is how to think about theme selection during a migration.
Don't lift-and-shift your problems
Your current design carries years of accumulated compromises: confusing navigation, a cluttered product page, a slow homepage. Recreating it faithfully on Shopify preserves all of that. A migration is a rare chance to fix UX and performance issues while you are rebuilding anyway, so treat the design as a decision to make, not a constraint to copy.
Theme performance is a real cost
Theme code is one of the biggest drivers of Core Web Vitals. A bloated theme with heavy scripts and poor structure will fail LCP and INP no matter how good the content is. Choosing a well-built, performance-minded theme, or building a lean custom one, is a performance decision as much as an aesthetic one.
Standard theme, customized theme, or custom build
There are three broad routes. A quality standard theme (Shopify's Dawn or a strong marketplace theme) is fast and cheap and fits many brands. A customized theme adapts one of those to your brand and requirements, the common middle path. A fully custom theme or headless build is for brands whose experience genuinely cannot be delivered otherwise, and it carries ongoing cost. Most stores are best served by the middle option.
Let data guide the design
If you have analytics on the current store, use it. Where do customers drop off, what do they search for, which pages convert? A migration paired with a UX audit lets you rebuild around evidence rather than guesswork, so the new theme fixes measured problems.
Plan content structure early
Themes assume a content structure, collections, metafields, page templates. Deciding this early means the migrated data lands into a theme that expects it, rather than forcing rework. This is especially true for large or configurable catalogs.
Theme selection sits inside the wider migration and launch process. Chosen well, the new theme is the most visible proof that the migration was an upgrade, not just a move.