Then normal Lua by itself would probably be fastest for you. Nothing makes me happier than writing native extensions for Lua. Its C API is such a pleasure to work with. With Python and JavaScript, writing native extensions is the worst most dismal toil imaginable, but with Lua it's like eating dessert. So if you know both Lua and C++ really well, then you're going to be a meat eating super programmer who builds things that go really fast.

I prefer using Python with pybind11. It makes writing new modules or embedding the whole interpreter quite simple.