Hi Mo, are you using UE5+? The functions the template uses are built into the Character class already, such as Jump. With that said, you can easily create the new Enhanced Input system in c++ and copy the few existing Input Actions over from the Blueprint. There really isn’t much that you would need to do to get what the template has into c++, so it is a quick transfer. Copying would be your best bet to convert into c++, and gives you more control. Also, you can not build a c++ class from a blueprint class, but you can build a blueprint class from a c++ class.
Edit: The Input Actions can be used simultaneously by c++ and blueprints, the only difference being you have to bind the IA in c++. Your issue however would require that you derive a c++ class from the BP character class, which like I mentioned, you can’t. Only works the other way around.