Thanks for your reply.
I think maybe the question was not well-posed from my end. What I am trying to do is create my own plugin and hence tools in the Rhino and a corresponding toolbar to accommodate them. For this, as you mention I will have to generate an RUI file. I know already how to make a new toolbar and add tools to it but I am struggling with adding specific functionalities to them. I want to have some leads for the script or macro editing for that. The video that you suggest is for existing tools in the workspace.
Apart from that, could you also tell me something about the second part of my initial question, different aspects and challenges in using C++ and C#.
Sorry for the naive questions, I am new too this.