Minimum order price — blocks checkout below this subtotal (shipping
not counted). Pro to newly set — grandfathered if already set.
Shipping fee — a fixed fee on every order (0 = free shipping).
Free shipping threshold — appears once a shipping fee is set; waives
it above this subtotal (after coupon discount). Same Pro/grandfathering
rule as minimum order price.
Default VAT % — pre-fills new products' VAT field (doesn't apply
automatically). Show VAT on storefront checkbox.