Answer 1

Visual Studio is good for UIs; start a winforms project, or WPF if you're feeling brave.

Answer 2

C# has in-built functionality for Windows Forms, and can be easily found when creating a new project on Visual Studio.

With C++, you'd want to use something like Qt, as it does not come natively to easily create Windows Forms, unlike C#.

Answer 3

In C#, I would use Unity as it is powerful, simple to use and as I do not really like this language :p
In C++, I would use SDL2 or OpenGl with GLFW but you can also use Qt creator or SFML