@asen85 Thanks for your message. No, in most cases you would not require an additional schema plugin unless you have some specific need or feature of structured data not offered in Yoast SEO.
You can find more details about the structured data that our plugins add here: https://developer.yoast.com/features/schema/overview/. We also have an in-depth guide on how to implement it on your website: https://yoast.com/structured-data-schema-ultimate-guide/
We have not officially tested any recommendable plugin for Schema. However, we suppose Schema plugins should be compatible with the Yoast plugin according to their compatibility document article here: https://schema.press/compatibility-yoast-seo/
However, since duplicated data is a concern, if you are using multiple plugins for structured data output you should test how the data appears using the Google Rich Results testing tool here: https://search.google.com/test/rich-results
