Integration of native libraries/SDK


starting to evaluating Xojo for a side project and I wondering what are the strategies to integrate Xojo with existing libraries and SDKs.
I am aware that Xojo plugins can be created to integrate existing libraries, but, as far as I have understood this is done using C++.
I am also aware about Declares that makes calling native API easy. But It’s not clear to me if I can use Declares for calling external libraries that should be linked with the Xojo apps.

Just to make a example: if I would like to interact with Google Drive APIs or Microsoft Graph APIs, I could use a target platform SDK (for example on MacOS Swift or Objective-C SDK) and call the SDK APIs wrapping with declares?

I know that I can use REST or maybe already existing Xojo plugins, but my question is general.
Could I mix Xojo code with Swift code for example? Or, still talking about macOS, if I have a Swift Framework library, can I call it’s API from within Xojo?

Thank you in advance