Hi, please be aware of two things: 1. Google search and Google News are two different things (I mean they behave differently with respect to sitemaps) and 2. there is no way to prevent Google to index certain pages by way of a sitemap.
First, Google News. What is your current news sitemap location? If you switch to this plugin, your news sitemap will live on /sitemap-news.xml which might need you to make Google News aware of that change, or at least put up a permanent redirection from the old URL to the new. You can use an excellent plugin like Redirection for that, which allows you to monitor redirection stats as well. Also, make sure to update your news sitemap location in Google Search Console. Once set up, you are now free to ex/include whatever type of content in your news sitemap and (at least in theory) Google News should respect that and only take what is in your news sitemap. If it does not, I suggest turning to the Google News Support forums, or maybe ask there in advance to be sure 🙂
Then the XML Sitemap. Same as above: make sure to update Google Search Console. Other than that, you should be perfectly fine. An XML Sitemap is just a tool to aid search engines to find stuff faster on your site. But once indexed, you will not be penalized for having different URLs in your sitemap (after switching plugins, I mean) or even when you stop having a sitemap at all… be aware that if some URLs are no longer in your sitemap, they will remain in the Google index (or if they are not yet there, Google will find them at some point) so if you explicitly wish to exclude certain pages/posts, you’ll need to use an SEO plugin that allows you to set a noindex meta tag. Major search engines will respect this flag and either not index that content or (at some point) remove it from their index. To speed that up, you can use your Search Console (both Google and Bing have this option) to remove certain URLs from the index.
Hope this helps 🙂
