Hi Vivek, I think your suggestions are good so I've voted them up. I can't tell you if or when such videos will be made, though. As for now, you can ask your questions under the appropriate video(s).

For  visualizations of 3d shapes you can try one of the programs of Peter Collingridge, like https://www.khanacademy.org/computer-programming/3d-surface-viewer-2/1092842126

For explanations about when to use which method, shell or disk, the blog entry here made sense to me: https://themathblogger.wordpress.com/2012/04/30/when-to-use-disk-method-versus-shell-method/