I use Dynamic Bones which costs money on the Unity Asset Store. There might be alternatives which don't work as effectively but I've not used them personally. If you don't mind the lack of physics you can just rotate the bones in the feelers/tail so they hang downwards instead.
According to the tutorials that I followed, the viewpoint should be just outside the eyes. Obviously this can also be dependent on the model as some may have additional features such as snouts or beaks which may obstruct the view when tilting the camera. I have not experienced such issues with this model as I do not have a VR headset to fully check but if you are able to correct any issues yourself then please feel free to do so. I am simply uploading these as and when I can as a matter of convenience for folks who enjoy Pokémon and want a model that works in a basic sense.
I'm trying to figure out 'snake' avatars myself. I can make generic rigs if I can get my hands on an animated model but that's pretty difficult. I'll keep trying though!
You need to download Cubed Unity Shaders for the texture to work. If not, try changing the shader on the textures in the material folder back to standard.