func_cpp style is functionally equivalent to
pointer_cpp in every way except for one. Instead of using function pointers directly, it uses inline functions in the headers. These forward the calls to the function pointers.
The only reason to use this style over
pointer_cpp is that it makes it easier for IDEs and other autocompletion tools to recognize a function call. Many such tools can handle function pointers, but if yours cannot, you can use this to give it the help it needs.