Shopify stores for fashion brands that sell the aspiration.

One that loads fast on mobile with large imagery, since apparel sells on photography and most of your traffic is on a phone. Look for lazy-loaded galleries, a quick-add that does not force a page load, and proper variant swatches. A premium theme configured well beats a custom build for most brands under a few thousand SKUs.

Shopify allows three options per product with up to 100 variants each on standard plans, which covers size, colour and fit. Use variant images so selecting a colour changes the photo, and a size guide as a metafield rather than an image so it is readable and indexable.

Yes. Store it as a metafield or metaobject and render it in the theme as a drawer on the product page. An app for this is a monthly fee for something a theme change does permanently.

Accurate measurements on the page rather than a generic chart, photography that shows fit on more than one body, and fabric and care detail written out. Most apparel returns are sizing, and sizing is a content problem before it is a logistics one.

Both, for different jobs. Collections are the indexable pages you want ranking — "women's linen shirts" — and should be built deliberately. Tags drive filtering inside those collections and should not each generate their own indexable URL.

A premium theme configured to your brand is days to two weeks. A custom theme is 3 to 6 weeks. A migration from another platform is 2 to 6 weeks depending on catalogue size.