To simply use a boolean result to select between two values of another type, I think a case structure is overkill. Using a "boolean selector" is easier and results in code that can be seen all at the same time. Here's an example of it in use:
Ignore the surrounding loop and associated shift registers, and focus on the boolean input to the selector. When it is true, the top numeric input appears on the output; when it is false, the bottom numeric input appears on the output. This works with relay constants just as well as it does with numbers.