Creating separate sitemap doesn’t give you any advantage. As for your question, there is no need for it.

Should AMP pages be included in sitemap?

AMP urls are supposed to be included in XML sitemaps. See https://developers.google.com/search/docs/guides/create-URLs.

How do I add a mobile URL to a sitemap?

Once you’ve created your Sitemap, log in to your Google Account and submit it using the Add a Mobile Sitemap page. Specify the markup language that the URLs listed in the mobile Sitemap serve. Once you’ve submitted the mobile Sitemap it will be listed on your My Sitemaps page as a “Mobile” type.

Do I need to submit my sitemap?

If you do not submit a sitemap, that means Google will access and crawl your website like you would expect, visit a URL and note down all links and then crawl those, note down new URLs, and so on.

What is mobile sitemap?

Mobile Sitemap Explained

This should be submitted independently to the search engines to enable them serve search requests from mobile devices better, then guide them to the pages of your site. Note that mobile sitemap has to only contain links to pages with mobile web content.