seo – Hierarchical vs flat sitemap

Your question is actually divided into a few categories, each of which has different considerations:

XML Sitemap
In your Sitemap, you can specify both the frequency of change and the priority ranking for the various pages. In this way, search engines can determine how important a page is on the site and how often it should be crawled for changes. Avoid listing duplicate content sites like / fashion / women / shoes and / fashion / shoes / women. In such cases, select a URL as the canonical URL that you want to send to search engines.

URL structure
By maintaining a minimum hierarchy in your URL structure for each page or for faceted search results, a search engine can index your website and display top-level category pages. (The search result of a department store can, for example, show the different departments.)

user experience
A menu with too much depth can lead to a bad user experience, as the user may be overwhelmed by the choices or simply tired of browsing through many navigation levels. A well-structured search interface with the most common categories as predefined filters will help you avoid an overly complex menu. Similarly, users can use breadcrumbs on the page to return to the top category or subcategory pages.

Look for products in Engjne Optimization
For each product on your site, consider adding schema microdata to your markup. That way, search engines can identify the individual products that are being offered for sale on your E-Comm site. See https://schema.org/product

Also, consider adding an RSS or XML feed and sending it to multiple sources to improve the reputation of your site.