Having reviewed popular websites there appear to be two different to structured data. Most sites incorporate an Organization type and a type to reflect the content of the page, Webpage or NewsArticle for example.
Some sites split these into separate blocks whilst others incorporate it using @graph. Whilst there doesn't seem to be an issue with either approaches what if a page reflects multiple types.
Say it is a Webpage but also contains a few FAQs. This would make it an FAQpage as well. The list could go on if we start incorporating images and videos. Can all of these be listed in the page's structured data and are there any SEO advantages or disadvantages in doing so.
Take a look at apple.com/arcade. Their approach is to use two structured data scripts, one for Organization and one for FAQpage to reflect that the page contains FAQs. Why do they not also have Webpage type to reflect the rest of the content on the page?
If you mean separate top-level multi-types in structured data for one content, then this is a content structure representation error. Every content of any web page is an HTML document. Each document has only one subject of content. In the main content, it is a good idea to use the H1 element to introduce the subject. In structured data, a top-level type is used to represent a subject. The content may have multiple sections/paragraphs. In this case, structured data can have branches with embedded types representing the topics of sections/paragraphs. Read more 1d. Embedded items of Schema and mainEntity(OfPage) property of Schema.
Clear structured data markup helps present the structure of the content in search results, which in turn helps users easily navigate the content and jump straight to their goal.