[banachtarski]

You may understand the mechanics of C++ linking (although I doubt it because including a header has nothing to do with linkage, I'm assuming you mean ADL, overload resolution, etc), but it doesn't seem you understand the mechanics of how C++ compilers are built and optimized. Furthermore, how many cpp units do you expect to require the Vulkan API? If it's much more than a few dozen, I would argue you haven't organized your engine well. Source: former graphics engineer.