This uses unity assetbundles, so, anything that uses the same format, and uses the same unity version, should technically be compatible (examples of this would be the old VRChat avatar files. or most unity games that would follow the same genre/work-logic).
In case you want to use vrm files, you will need to find a way to import that into unity, and then use the tools that are provided when you download VCRA to export it (you can call it our own SDK if you are looking for a more familiar terminology). To export, there is a HOW-TO document with the files in case you need to follow some instructions.