Hi
I do not know the extension of the Music Studio instruments and I would not know how to respond correctly.
But I know you can use the interapp function, without the need for audiobus with other programs. I use KV331 and DRC, and so you have more possibilities. In this case you would play the instrument from MS, but to play it you will need to activate the native application of that instrument in question. Then you will record it in an audio file and incorporate it into your song.
Another option is to take samples of the instrument you want to use by incorporating it into your instrument catalog. That instrument will always be available even if you no longer have the native application with which it was created.
Look at this video.
Good luck