Having the same information on multiple sites is an SEO and no-no. I don’t recommend it. I have a (I think broken, but I’ll fix it Real Soon Now) theme component that will change the home page depending on what group someone is in so you could set their group according to a custom field you get when they create their account to set their hole page to the category for their favorite product.
If your don’t care about having your site indexed, you can look at the web_only template that redirects and add to your yml to un-do that. I think that Setup Multisite Configuration with Let’s Encrypt and no Reverse Proxy offers an example.