I make 3d Avatars for VR applications like VRChat and VSeeFace as a hobby.
Find all my links at squirrelbite.com.

The single relevant format for VR & V-Tubing avatars is a .unitypackage that contains a scene with a setup somewhere.

There is no interoperability for avatars. And the least horrible format for 3d models is unfortunately fbx.
Using those avatars as an end-user is prohibitively difficult as it requires the use of a Game-Engine like Unity.

With the STF project, I'm trying to create an easily extensible interchange format for 3d models.
STF should be able to easily host an extension for application agnostic & fully featured VR & V-Tubing avatars.

You can view my progress in the STF - Scene Transfer Format Repository