Blendshapes/Keyframes vs Animation Clips

Hey there! I'm developing a game using Unity and a bunch of editor extensions I've made. I'm also animating the characters in Blender. I was hoping that I would be able to have keyframes or blendshapes exported from Blender to Unity and further manipulate them within the engine and code.

I suppose my first question is: Is there a difference between how Unity might tween between blendshapes and how Blender tweens between keyframes(sorry if that's outside the scope of this forum)? Additionally: would there be any performance issues? Especially since, in this case, I'd be using blend shapes over an entire character model + facial animations?

Ideally I'd like to have keyframes/blendshapes that I create in Blender then be able to manipulate them in Unity. I'm designing a competitive fighting game and each skill is broken up into frames. Each frame has hitboxes and events for controlling states and velocities, etc. I'd also like to assign keyframes/blendshapes to those frames rather than just play an animation clip for that skill. Specifically with a simple integer referencing the keyframe/blendshape. This would allow me to tweak the skills more easily with the animations. I'd further like to be able to control a timing curve between the keyframes/blendshapes and crossfade them.

Any thoughts or suggestions would be greatly appreciated. Even some that are different from the implementation I requested. Thanks!