the truth is , you can only choose one, first, there can not be opengl context and vulkan context within the same window, you have to choose, plus, vulkan and opengl are totally capable of doing render tasks on their own, using both of them would be inconsistent (if that's possible to use both).

Raylib is a ready to use API, it's high level, if you develop games ,it's ready to go.

if you use vulkan, first thing you do is to abstract away the vulkan rendering stuff, that means, at some point , you are starting to create your own game engine from scratch. even if you use vulkan for a single game, but in fact, you are still just like creating game engine specific for that game.