I am quite familiar with 360 video rendering in unity as I was working on scene creation using panorama image last semester. I was also using spheres and rendered the 360 painting inside but with a flipping normal shader script which allows the shader to be flipped. I think what I learned in class, using Blender or other 3d modeling software to revert the normal is more efficient and easy to execute, as sometimes I got the capability issue when I use this special shader to render the video or image with the alpha channel.
Another thing caught my eye is that render 360 videos or images using skybox of the camera produces less distortion at the poles compared to rendering inside spheres. It is more natural to view the 360 content using this skybox approach. I did some research in the unity community, and it suggested that the issue might be caused by the shader which cannot handle equirectangular images very well. By writing a specialized shader or tilting the texture attached to the rendering material, this distortion issue could be alleviated.
Adding 360 audio in unity is a really new and interesting concept for me. REAPER looks a little bit overwhelming for me as I am not familiar with any audio-editing software or workflow, but Resonance audio for unity gives me hope, thanks to its great documentation. I really enjoy the visual representation it has to let me understand how to manipulate direction, sharpness, and range. There are also lots of useful scripts and templates providing a good start point for 360 audio in unity.