Search results signature is one of the Search Box rendering properties which can be convenient when you have more than one search result rendering on the page.
To show different search results (with different scope) on the same search result page, you need to do the following:
1. Search Box Configuration: To edit the default behaviour of the search box, open the Control Properties dialog box and edit the Search results signature field: enter the unique signature of a specific Search Results rendering to limit the search results. This will be convenient when you have more than one search result rendering on the page. In your case, you’ll be having two search results rendering on the search page. Just placed all the Search Results signatures in the Search results signature separated by “,”.
2. Search result configuration: Open the search page in experience editor and edit the Search Criteria for both search result boxes. eg
- First search box
- second search box
Refer to this blog for more details: https://sitecorewithraman.wordpress.com/2021/08/10/sxa-multiple-search-results/