Is there any way to integrate all krpano and plugin xml files and js files into one xml file
That's possible, but would need to be done manually.
And the relative url paths in the related/included xml files would need to be adjusted of course.
To make the xml file smaller for faster loading, it's additionally also possible to encrypt it (using the Encrypt Tool) - together with the encryption the file will be also compressed.
Best regards,
Klaus